Genetic Engineering of Plants OLD News
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During 1990 many commercially important crops began to be genetically modified. These include Indica varieties of rice and maize. Fertile wheat and sorghum plants were recovered from protoplast suspension, therefore genetic modification of these plants via protoplast transformation is now possible (Vasil, I.K. (1990) "Transgenic cereals becoming a reality", Biotechnology 8: 795). For the production of transgenic maize, high-velocity microprojectile guns shooting DNA into cells can be used (Biotechnology 8 (1990), 833-839). Methods for making pollen sterile have been developed, which are very useful for plant breeding (Peacock, J. (1990) "Ways to pollen sterility," Nature 347: 714-715; TIBS 15 (1990), 453-4). This is very important for the hybrid seed industry, who want to be able to control pollination. Agrobacterium has been used to transform grapevines, to make transgenic grapes, which should be useful in this crop which is difficult to breed using conventional methods (Biotechnology 8 (1990), 1041-1045).
The genes involved in the initiation of nodule formation in legumes, with bacteria such as Rhizobium that are involved in nitrogen fixation, are being investigated. The substance produced by Rhizobium , called tetraacetylglucosamine, induces root hairs in alfalfa at concentrations the order of a million times lower than the active concentrations of other plant hormones (Biotechnology 8 (1990), 897). An increase in the ability of plants to form nodules could increase their nitrogen fixing ability, and thus growth. This might be possible by genetic manipulation of such genes.
Researchers have induced the formation of nitrogen-fixing nodules in nonlegumous plants, including rice and wheat (Science 250: 910-912). For a recent review of the biochemical understanding of the enzymes involved in nitrogen assimilation in plants see Crawford, N.M. & Campbell, W.H. (1990) "Fertile fields", The Plant Cell 2: 829-835.
A potentially important crop variety already made using genetic technology is cotton: Perlak, F.J. et al. (1990) "Insect resistant cotton plants", Biotechnology 8: 939-943 (they used Bacillus thuringiensis insecticidal protein genes to control the major cotton pests). Another recent paper of plant genetic engineering is Jorgenson, R. (1990) "Altered gene expression in plants due to trans interactions between homologous genes", TIBTECH 8: 340-2.
The sensitivity of plants to chilling is an important area of research and could extend the range of environments that plants are grown in. Wada, H. et al. (1990) "Enhancement of chilling tolerance of a cyanobacterium by genetic manipulation of fatty acid desaturation," Nature 347: 200-203, describe the increase in cold tolerance of blue-green algae by altering the membrane fatty acids, and the work may be extendable to higher plants. Research in developing plants that can cope with another environmental extreme is reviewed by McCue, K.F. & Hanson, A.D. (1990) "Drought and salt tolerance: towards understanding and application", TIBTECH 8: 358-62.
The use of baculoviruses for plant insect protection has been advanced by the expression of the Bacillus thuringiensis insecticidal protein gene in baculoviruses. This should enable much more rapid killing of the insects who become infected (Martens, J.W.M. et al. (1990)"Insecticidal activity of a bacterial crystal protein expressed by a recombinant baculovirus in insect cells", Appl. & Env. Microbiology 56: 2764-2770). A summary of the efforts to search for search for plant pest resistance genes is in Nature 347 (1990), 517.

The oil palm is the second most important worldwide crop used in the production of vegetable oil. A review of the breeding of oil palm is A.C. Soh (1990) "Oil palm breeding - breeding into the 21st century", Plant Breeding Abstracts 60: 1437-44. Most of the oil palm plantations are in South East Asia , Central or Western Africa and Latin America, and it is an easily grown high yielding crop, and is important to the economies of several developing countries. The breeding improvements using standard breeding are still quite high, about 15% per ten years. Clonal propagation is being used to increase yields and alter oil fat composition, and disease resistance. There is a lack of basic genetic and biochemical knowledge which will delay the application of genetic engineering.
Chimeric apple trees have been made, by grafting with cuttings that were genetically modified by Agrobacterium rhizogenes : C.Lambert & D.Tepfer (1991) Biotechnology 9: 80-83. The roots were transgenic but not the stems, therefore any fruit will not be transgenic and not subject to special food safety examination. The rooting efficiency was increased and such trees are of considerable interest to fruit growers. Another species that has been examined with this approach is olive, and others will no doubt follow.
A review on the use of cell fusion techniques for genetic improvement is K.Glimelius et al. (1991) "Gene transfer via somatic hybridization in plants" TIBTECH 9: 24-30. It also discusses methods to improve the transfer of cytoplasmic traits.
A technique to allow nonleguminous crops to harbour nitrogen fixing bacteria may be possible to develop: NS (8 Dec 1990), 4. Wheat that are treated with a very low concentration of the herbicide 2,4-D have altered root development that allows bacteria of the Azospirillum species (but not Rhizobium ) to enter the plant and multiply. In experiments on young plants the nitrogenase activity was increased 50 fold. The use of other chemicals to alter root formation is also being investigated.
A book that includes some coverage of plant-microbe relationships is J.P.Nakas & C.Hagedorn, eds., Biotechnology of Plant-Microbe Interactions (McGraw Hill 1990), which receives a quite negative review in TIBTECH 9 (1991), 38. Another recent book is S.C.Witt, Biotechnology: Microbes and the Environment (Center for Science Information 1990), which is aimed at the public audience or the nonspecialists involved in decision making. For a review see TIBTECH 9 (1991), 37.
A review of the improvement of lactic acid bacteria by the use of genetic selection and engineering is L.L. McKay & K.A. Baldwin, "Applications for biotechnology: present and future improvements in lactic acid bacteria", FEMS Microbiology Reviews 87 (1990), 3-14. Most of these bacteria are used in the dairy industry, but they are also important in fermentation of other food products. The growing knowledge about their genetics will be increasingly used to develop strains that alter the flavour and improve the quality of the food products. One possible use is to make lactose-depleted dairy products which could be consumed by people who have lactose intolerance, so that they could then safely consume milk, or yoghurts. The fermentation processes could be speeded up by the alteration of different enzyme's relative activity. The bacteria can be made more disease resistant, especially to bacteriophage.

In addition to the nuclear genome, plant cells have many important genes in their chloroplast genomes. A paper on the manipulation of this genome is K.L. Kindle et al (1991) "Engineering the chloroplast genome: Techniques and capabilities for chloroplast transformation in Chlamydomonas reinharditii ", PNAS 88: 1721-5. Another technical paper describing a method to isolate sequences near genes of interest is G.B. Martin et al. (1991) "Rapid identification of markers linked to a Pseudomonas resistance gene in tomato by using random primers and near-isogenic lines", PNAS 88: 2336-40.
There is much pressure in California to avoid the use of pesticides in farming; D.Charles, "California's war on pesticides", NS (2 March 1991), 39-43. It also includes comment on the political proposal that was voted against in the California state elections called Big Green . 80% of the pesticides used in the USA are herbicides, but there is more concern over insecticides, especially those that are carcinogenic. There are many cases of poisoning of farm workers, who may often be migrant workers who are not informed in the safe handling of these dangerous chemicals. There is much harm done in many developing countries where there are usually much looser regulations, or none at all, yet widespread use of dangerous pesticides. In Indonesia the use of most pesticides in rice has been banned and education on biological control provided to farmers. There is also research into using GMOs with natural pesticides such as the Bacillus thurengiensis insecticidal protein. The environmental concerns push the case for rapid introduction of more environmentally friendly methods of pest control, such as those using GMOs and altered farming methods using biological control.
For more on biological control see A.&P.Fullick, "Biological pest control", NS (9 March 1991), "Inside science" supplement 43. The is also interest in using the fungi Trichoderma viride for control of plant disease, including using genetically modified strains; Letters in Applied Microbiology 12 (1991), 59; Biotechnology 9 (1991), 315.
To obtain data on the incidence of pest resistance to pesticides may be impossible because of commercial secrecy; NS (23 Feb 1991), 13. It is very difficult to judge how large a problem it is, but it would be useful data for predicting resistance from the use of GMOs.
An extensive review and discussion paper is a report from the Ecological Society of America, J. Lubchenco et al. (1991) "The sustainable biosphere initiative: an ecological research agenda", Ecology 72: 371-412. The subject of sustainable development is of great importance for the future, and a range of topics are discussed.
The development of alfafa mosaic resistant alfalfa plants using Agrobacterium as a gene vector to transfer coat protein genes is described in Biotechnology 9 (1991), 373-7.
A literature review on an area of microbial fermentation is M.R.Ladisch (1991) "Fermentation-derived butanol and scenarios for its uses in energy-related applications", Enzyme Microbial Technology 13: 280-3. A comment on the growing commercial bioreactor use is in Biotechnology 9 (1991), 338-41.

A review on plant lipid metabolism, and the way that it may be altered by genetic engineering is C.Somerville & J.Browse, "Plant lipids: metabolism, mutants, and membranes", Science 252: 80-7. Among crop plants there is a limited diversity of different lipids accumulated as storage products, but in wild plants a wide variety of fatty acids has been found, some of which are of potential commercial use. They could be produced in industrial quantities if the genes were inserted into suitable crops or cell systems. The fatty acids in the membranes of cells also determine how the plants respond to environmental stress, so by altering the fatty acids in the membranes the environmental tolerance could be varied, for example, to lower or higher temperature extremes. Many experiments in the model plant species Arabidopsis are discussed. A switch to different oils that can be made in plants is of potential importance in the switch to renewable energy resources. It may also be used to alter food quality.
The number of species of plant that have been transformed and grown from culture increases. Transgenic plants of the nitrogen-fixing tree, Allocasuarina verticillata , have been grown; Biotechnology 9:461-6. This tree is a member of the family Casuarinaceae, which as fast growing trees will be important in efforts to reforest desert areas of the world, and to provide fast-growing wood sources.
A system for monitoring intrachromosomal homologous recombination in plants is described in EMBO J. 10: 1571-8. They used a multimer of cauliflower mosaic virus sequences as a marker.
The number of genetically modified plants that are being field tested is rapidly increasing. A look through the list of releases from the USDA (as of early May they had 173 release permits issued or pending) makes interesting reading. One example is the development of bruise resistant Russet potatoes that have a gene inserted to reduce the level of tyrosine have been glasshouse tested, and are now in the field for a test of the effect on the bruising.
Of general interest see S.Young, "How plants fight bacteria", NS (1 June 1991), 41-5.

The research on the development of new coloured flowers is producing some results. Researchers from DNA Plant Technology Corp. in the USA are field testing white chrysanthenums; Science 252: 1613. They added a nonfunctional duplicate of the normal pigment gene, which suppresses the original gene's expression. The plants have high productivity and are disease resistant, unlike the current white chrysanthenums. Meanwhile, research on the pursuit of a blue rose continues.
Research on the regulation of fruit ripening is progressing. One approach is to control the level of ethylene, the ripening hormone, that is produced. One of the enzymes in the synthetic pathway of ethylene, is investigated in a report; D.C. Olson et al., "Differential expression of two genes for 1-aminocyclopropane-1-carboxylate synthase in tomato fruits", PNAS 88: 5340-4. Also using tomatoes, but with a different problem, that of preserving taste and texture after freezing of crops, is the application for field testing of DNAP for tomatoes that express the winter flounder "antifreeze" protein; Biotechnology 9: 501.
The transformation of cereals continues to become more efficient. A report is V.Vasil et al., "Stably transformed callus lines from microprojectile bombardment of cell suspension cultures of wheat", Biotechnology 9: 743-7. A comment on the genetic origins of corn is in Science 252: 1793.
A report on virus resistance is K.Ling et al., "Protection against detrimental effects of Potyvirus infection in transgenic tobacco plants expressing the Papaya Ringspot virus coat protein gene", Biotechnology 9: 752-8. Broad spectrum protection was obtained in this study. Some examples of transgenic crop research in the USA are given in Science 253: 33. A new book Molecular Approaches to Crop Improvement, Plant Gene Research, eds. E.S. Dennis & D.J. Llewellyn (166pp., US$64, Vienna: Springer Verlag 1991).
Research into forestry is mentioned in Science 252: 1469. Black cottonwood is the fastest growing hardwood of Washington state area, and hybrid trees are being tested that are twice as fast growing as the parent trees. These trees may be used as low cost sources of biomass, but still take many years to grow to maturity. The price of alcohol from woody sources will be competitive with petroleum products in the near future, and by the time those trees grow it will be a clear advantage. This is good news for the world's energy needs.

A joint announcement has been made by Calgene Pacific and Suntory that they have inserted a blue pigment gene from petunia into a rose seed, in the effort to make a blue rose; GEN (Nov/Dec 1991), 10.
There have been transgenic tomato plants made that soften more slowly (SG 120), now antisense techniques have been applied to show that it is the hormone ethylene which is the cause of senescence; P.W. Oeller et al., "Reversible inhibition of tomato fruit senescence by antisense RNA", Science 254: 437-9; H.J. Klee et al., "Control of ethylene synthesis by expression of a bacterial enzyme in transgenic tomato plants", The Plant Cell 3: 1187-93. This raises prospects for the control of fruit spoilage. On the use of antisense techniques in plants, and the mechanism of interaction with plant genes see TIBTECH 9: 122-3, 266-7.
In Japan, a more tasty variety of rice has been reportedly made by Mitsui BioResearch lab in Tsukuba; Asahi Newspaper (17 Dec). The Japanese taste buds prefer a low amylose level. The normal indica variety has 25-30% amylose (in starch), but the best tasting varieties have 18-20% amylose. Using genetic engineering they have made a variety, based on the Nihonbare variety, with amylose at 10-15%. However, it is still to be tasted, and must go through many stages before it will be field tested, and it may be years before it can be eaten, depending on when the regulatory authorities decided what regulations will apply to commercial crops and foodstuffs.
Resistance to RNA viruses in plants has been obtained for many positive-strand RNA viruses. The first case of resistance to a negative strand RNA virus is reported by J.J.L. Gielen et al., "Engineered resistance to tomato spotted wilt virus, a negative-strand RNA virus", Biotechnology 9: 1363-7. They used insertion of a gene for the viral nucleocapsid protein, an internal RNA binding protein. Transgenic tobaccos with a chitinasae gene were found to have enhanced resistance to the fungal pathogen Rhizoctonia solani ; Science 254: 1194-7. Also on plant disease resistance see TIBTECH 9: 373-4.
A short review on some applications of plant genetic engineering is in The Plant Cell 3: 1141-2; an extensive review on gene transfer to plants is I. Potrykus, "Gene transfer to plants: Assessment of published approaches and results", Annual Review Plant Physiology and Plant Molecular Biology 42: 205-25. Breeding to select lines that are cold resistant is described by R.S. Malhotra & K.B. Singh, "Gene action for cold tolerance in chickpea", Theor. Applied Genetics 82: 598-601.
A recent book is Lawrence Busch et al., Plants, Power, and Profit. Social, Economic, and Ethical Consequences of the New Biotechnologies (Basic Blackwell 1991, 275pp.). It looks at the examples of wheat and tomatoes, and the general scope of biotechnology.
Papers on the transformation and production of fertile transgenic plum; Biotechnology 9: 953-7; melon; Biotechnology 9: 858-63; and carnation; Biotechnology 9: 864-8; have recently appeared. Reviews of books in a series Plant Biotechnology Series, Vol. I and II ( Blackie/Chapman & Hall 1991) appear in TIBTECH 9: 446. Another review, of a book on tissue culture in leguminous and oilseed crops is in TIBTECH 9: 399.
An alternative gene delivery system to microparticles (biolistics) has been used on wheat. It involves transferring the genes in microdroplets contained in a gas stream; C. Sautter et al., "Micro-targetting: high frequency gene transfer using a novel approach for the acceleration of microprojectiles", Biotechnology 9: 1080-5. For wheat the transferred E.coli b -glucuronidase gene was transiently expressed in 3% of cells, and in tobacco stable transformation with neomycin phosphotransferase gene occurred in about 0.1% of exposed cells. Also on gene targeting, but using T-DNA of Agrobacterium to transfer DNA to the chloroplast genome of tobacco see Biotechnology 9: 1103-5.
Also of significance, is techniques to allow the deletion of marker genes once the desired gene has been inserted into plants; Science 254: 1457. This may lower the level of concern about the presence of antibiotic resistance genes, though regulators may still decide that the presence of genes for resistance to neomycin and kanamycin is not significant.
On the subject of nitrogen fixation, and the growth of Rhizobium with non-legume plants see TIBTECH 9: 79-80.
Of related interest, a review of RNA splicing in plants is in The Plant Cell 3: 1045-7. On chromosomal first aid, see Cell 67: 645-7.

The Australian company Calgene Pacific estimates that it will be marketing blue roses by 1997, after isolating a suitable blue pigmentation gene from delphiniums. They recently also grew carnations with a gene for extended life; Nature 352: 653. I wonder how popular flowers with extended lives will be with flower shops? A review on the genetic understanding of flower development is E.S. Coen & E.M. Meyerowitz, "The war of the whorls: genetic interactions controlling flower development", Nature 353: 31-7.
On viral resistant plants see F. van der Wilk et al., "Expression of the potato leafroll luteovirus coat protein gene in transgenic potato plants inhibits viral infection", Plant Molecular Biology 17: 431-439. This virus causes an annual world-wide reduction of potato productivity of about 10%, therefore this strategy for making resistant potatoes could be very useful.
On methods of gene transfer see; A.C.M.Brasileiro et al., "An alternative approach for gene transfer in trees using wild-type Agrobacterium strains", Plant Molecular Biology 17: 441-52. The tree species best transformed were Poplar and wild cherry, and gall formation occurred on micropropagated tree shoots, thus avoiding the need for regeneration of seedlings from transformed callus. A paper on mutant Agrobacterium strains is PNAS 88: 6941-5. Another paper is C. Franche et al., "Transient gene expression in cassava using high-velocity microprojectiles", Plant Molecular Biology 17: 493-8. Transient gene expression is useful for a fast initial screening of useful genetically transformed plants, which can then be made permanent by the more time-consuming methods for production of stable transgenic cassava strains. A simple technique for production of transgenic plants is described in Li-Juan Zhang et al., "Efficient transformation of tobacco by ultrasonication", Biotechnology 9 : 996-7. Transgenic tobacco plants expressing the kanamycin resistance and GUS genes were produced at 22% production efficiency. Another method for genetic transformation is described in P. Christou et al., "Production of transgenic rice (Oryza sativa L) plants from agronomically important Indica and Japonica varieties via electric discharge particle acceleration of exogeneous DNA into immature zygotic embryos", Biotechnology 9 : 957-62. On the efforts to identify new genes in plants, in order to be able to use them for genetic engineering see comment on the Plant Gene Expression Centre in California; Science 253: 1465.
One approach to improving the growth of plants, or the production of specific compounds in plants, is to target the rate-limiting enzyme steps, to increase the production of certain substances made through the action of those enzymes. This approach is described in S. Herminghaus et al., "Expression of a bacterial lysine decarboxylase gene and transport of the protein into chloroplasts of transgenic tobacco", Plant Molecular Biology 17: 475-86.
The production of specific compounds in plants is a goal of many researchers, see J. V. Oakes et al., "Production of cyclodextrans, a novel carbohydrate, in the tubers of transgenic potato plants", Biotechnology 9 : 982-6. The starch in the tubers was converted to the high value products, but only at the equivalent of up to 0.01% conversion.

Insect Resistance to Bt toxin, and Pest Resistance Very serious concerns have arisen over the growing number of cases where insect resistance to the insecticidal protein of Bacillus thurengiensis (Bt). Bt toxin is already entering the commercial market in the USA, with the MVP and M-Trak pesticide delivery systems (EEIN 1: 59), in addition to the uses of Bt toxin for many years in other applications, as bacterial spores. It is the key to resistance of many transgenic plants that have been engineered to have insect resistance. Some type of management system is required, such as mixing resistance seeds with some non-resistant seeds so that the selection pressure on the insects to develop resistance, is reduced.
Resistance has been found in Hawaii, in three populations of diamond-back moths, after farmers used multiple doses of Bt on watercress and cruciferous vegetables. There are also reports from Florida, New York, Japan, Philippines, Thailand and Taiwan; TIBTECH 9: 177-9; Science 254: 646; Biotechnology 9: 1319. It is not known who, if anyone, will regulate the careful management of Bt toxin. It is very important that farmers think of the longterm implications, and don't use excessive doses of Bt or Bt toxin, and use some strategy for reducing the selection pressure on insects. Currently Bt products have a world market of US$50 million, 1% of the total insecticides, but this should expand, so companies are also concerned, as are environmentalists who want to reduce the use of chemical pesticides.
On the mechanism of resistance see S.C. MacIntosh et al., "Binding of Bt proteins to a laboratory-selected line of Heliothis virescens ", PNAS 88: 8930-3. The Bt toxin specifically binds to brush border membrane vesicles of both susceptible and resistant insect midgut epithelial cells, but the binding specificity was different. Also on Bt toxin, see N.B. Carozzi et al., "Prediction of insecticidal activity of BT strains by polymerase chain reaction product profiles", Applied & Environmental Microbiology 57: 3057-61; J. Li et al., "Crystal structure of insecticidal d -endotoxin from Bt at 2.5Å resolution", Nature 353: 815-21.
On the general use of pest control with genetically engineered plants see K.J. Brunke & R.L. Meeusen, "Insect control with genetically engineered crops", TIBTECH 9: 196-200. There are several other pest control genes. On improvement of the efficiency of baculoviruses see D.R. O'Reilly & L.K. Miller, "Improvement of a baculovirus pesticide by deletion of the EGT gene", Biotechnology 9: 1086-9; B.F. McCutchen et al., "Development of a recombinant baculovirus expressing an insect-selective neurotoxin: potential for pest control", Biotechnology 9: 848-52; also on baculovirus see Science 254: 1388-90.
A gene conferring protection against sap-suckers has been isolated from snowdrop flowers (Galanthus nwalis ); NS (14 Dec), 24. The isolated lectin kills brown plant hoppers, which damage rice in Japan and South East Asia. It was found by researchers at Agricultural Genetics in Cambridge, and researchers at Durham University. It has been transferred to lettuce and tobacco, via Agrobacterium . They are attempting to get specific expression of the protein in the phloem. They intend to provide it free or very cheaply, to developing nations who cannot pay for it.

A short review article on the range of plants that have been genetically engineered, and how this may sustain the world food supply, is R. Fraley, "Sustaining the world food supply", Biotechnology 10: 40-3. A list of 47 plants is given, which is useful. The range of new varieties (written in a business tone, so they are called "products") is discussed, and the current status of their research. The barriers to commercialisation are also discussed.
A list of some research in plant biotechnology in Midwestern USA is in Science 255: 25. It includes mention of research that has led to the localisation of the plant regeneration genes.
A technique for cutting out unwanted genes after transfer is E.C. Dale & D.W. Ow, "Gene transfer with subsequent removal of the selection gene from the host genome", PNAS 88 (1991), 10558-62; NS (1 Feb 1992), 28. The question of whether selectable marker genes are safe for use in plants is discussed in Biotechnology 10: 141-4. They consider that such genes present no special risk to humans or the environment. On the use of plant viruses for gene vectors see Science 255: 291.
A further herbicide resistant plant has been made. One that expresses an enzyme to convert the common herbicide cyananide (H2NCH) into urea, making the plants herbicide tolerant; NS (4 Jan), 11.
On the relationship between Rhizobium and legumes see P. Roche et al., "Molecular basis of symbiotic host specificity in Rhizobium meliloti : nodH and nodPQ genes encode the sulfation of lipo-oligosaccharide signals", Cell 67: 1131-1143.

In the future it is expected that genetically engineered plants will be used to produce bulk enzymes for industrial use, replacing the use of microorganisms as a source of enzymes for some applications. Important to the enzymatic breakdown of starch is the alpha-amylase, and it has been produced in the seeds of tobacco, which were directly used in enzymatic reactions; J. Pen et al., "Production of active Bacillus lichenformis alpha-amylase in tobacco and its application in starch liquefaction", Biotechnology 10: 292-6.
The results of three years of field trials of transgenic viral resistant potatoes which show that such varieties are already commercially viable is E. Jongedijk et al., "Increased resistance to potato virus X and preservation of cultivar properties in transgenic potato under field conditions", Biotechnology 10: 422-9. The potatoes stably expressed the coat protein gene of potato virus X throughout the growing season, while retaining their characteristic cultivar traits. Gene transfer to apricot has been reported, and saplings were grown from the transformed cells; Plant Cell Reports (March), NS (14 March 1992), 14. The gene transferred was designed to protect the trees against plum pox virus which causes Sharka disease, very common among stone fruits of Eastern Europe and Mediterranean countries.
Another approach to pest resistance in plants is to enhance the expression of naturally occurring ribosome-inactivating proteins (RIPs). RIPs are enzymes (N-glycosidases) which cleave the RNA of some ribosomes (those of pests in this case), controlling the pest. Researchers have put one RIP under the control of a wound-inducable promoter, so that when the plant is wounded the RIP is made, which stops the growth of pests; J. Logemann et al., "Expression of a barley RIP leads to increased fungal protection in transgenic tobacco plants", Biotechnology 10: 305-7. A review on uses of RIPs is in Biotechnology 10: 405-12.
Various sugarbeet varieties have been made tolerant to the herbicides glufosinate-ammonium and sulfonyl-urea compounds; Biotechnology 10: 309-14. The photosynthetic conversion of light energy into chemical energy is dependent on the absorption of photons of particular wavelengths. The absorbance bands of photosynthetic complexes in a purple-green bacteria, Rhodobacter sphaeroides have been shifted by site-directed genetic modification of the component molecules; Nature 355: 848-50.
In March 1992, Kirin Breweries Ltd., of Japan, applied for a patent under the Seeds and Seedlings Law on a variety of Turkish Bell Flower containing a bacterial gene which makes the plants small (from 1m to 20-60cm high), doubles the flower number and time of blooming; Asahi newspaper (26 March 1992), 8.
The host range (which determines which insects are killed) of the insecticidal bacteria Bacillus thuringiensis can be altered, and many naturally occurring variants are found; Biotechnology 10: 271-5. Description of how to expand this is; D. Lereclus et al., "Expansion of insecticidal host range of Bacillus thuringiensis by in vivo genetic recombination", Biotechnology 10: 418-21; M.M. Lecadet et al., "Construction of novel Bacillus thuringiensis strains with different insecticidal activities by transduction and transformation", Applied & Environmental Microbiology 58: 840-9. On the production of the Bt toxins in aquatic microbial species, Caulobacter cresentus , see Applied & Environmental Microbiology 58: 905-10. The advantage is that this aquatic species will last longer than Bt spores in water, where mosquito larvae reproduce.
Further biopesticides are being discovered which will lessen dependence on Bt; Science 255: 1070-1; Biotechnology 10: 378. Any pest management needs careful design to slow the rate of pests developing resistance to the pesticides; Science 255: 903-4; SA (March), 88; F. Gould, "The evolutionary potential of crop pests", American Scientist 79 (1991), 496-507.

Baculoviruses are one of the methods that may be developed as alternative insecticides, and a review is in Chemistry & Industry (6 April 1992), 250-4. Some of the registered preparations are already well established commercial products, and genetically engineered versions can be expected to be commercialised soon also. An example of a research paper describing results of how one such gene may be transferred to baculoviruses is M.D. Tomalski & L.S. Miller, "Expression of a paralytic neurotoxin gene to improve insect baculoviruses as biopesticides", Biotechnology 10: 545-9. The insertion of insect juvenile hormone gene into baculoviruses did not, however, affect the insecticidal properties; A&EM 58: 1583-91. For comments on the new biological pesticide products see NY Times (16 June 1992), D1, D17.
Another major route of insect resistance is expression of Bt genes, and a method for controlling the expresssion of such genes is described in S. Williams et al., "Chemical regulation of bacillus thuringiensis d-endotoxin expression in transgenic plants", Biotechnology 10: 540-3. The Bt gene is turned on by the signal chemical, and such variable expression may be useful, for example you may turn off the gene close to harvest to reduce the levels of the endotoxin in the edible product. On the design of insecticides, including chemical insecticides see TIPS 13: 236-41.
Fertility can be restored to male sterile plants using a chimeric ribonuclease-inhibitor plant; Nature 357: 384-8. The production of male sterility may be useful in the production of hybrid varieties. Efforts should be made, however, to make plants that are fertile so that farmers are not dependent upon seed companies. The crop used in this example was oil seed rape, a comment on the future of crops is in Nature 357: 358.
The use of hairy root cultures of plants as chemical factories is reviewed in Chemistry & Industry (18 May 1992), 374-7. The production of antibodies in plants is reviewed in Chemistry & Industry (1 June 1992), 406-8. The expression of antibodies may also have other useful traits such as modulation of herbicide sensitivity, by binding to antibodies. One can think of numerous applications of the introduction of modified antibodies in plants for binding substances and altering and introducing metabolic routes. Another protein sweetener has been produced in plants, L. Penarrubia et al., "Production of the sweet protein monellin in transgenic plants", Biotechnology 10: 561-4. This protein is about 100,000 times sweeter than sugar on a molar basis, and they transferred the gene to tomato and lettuce plants. Not so tasty, but also very useful is the production of plastics in plants (SG 118), Y. Poirier et al., "Polyhydroxybutyrate, a biodegradable thermoplastic, produced in transgenic plants", Science 256: 520-3. They introduced the genes into Arabidopsis thaliana , producing granules similar in size to those which accumulate in bacteria.
A conference review of the advances in plant genetic engineering and production of various products is in Science 256: 770-1. A series of papers are in Plant Molecular Biology 19 (May 1992), including reviews of the use of Agrobacterium (15-38), of manipulation of fruit ripening (69-87), of disease resistance (109-122). On the genes that regulate plant development see Plant Science 83: 115-26. A review of the means that oilseed crops can be modified for non-edible products is in TIBTECH 10: 84-7. They offer much promise for reducing dependence upon fossil fuel oil reserves, and by genetic engineering particular oil products can be accumulated in the seeds to lessen the refining process required after harvest.
A review of the genetic engineering of cotton is in TIBTECH 10: 165-70. Long term goals include modification of the fibre characteristics. To date most research has been on insect resistance and herbicide tolerance, plus environmental stress tolerance. Related to temperature tolerance is a paper, N. Murata et al., "Genetically engineered alteration in the chilling sensitivity of plants", Nature 356: 710-3. They altered the fatty acid metabolism of tobacco, and by altering the ratio of saturated to unsaturated fats in the membranes, it is possible to alter the temperature tolerance.

The USDA is supporting research projects to map the genetic material of major crops, and the 1992 budget for plant genome research is US$10.5 million; GEN 12(10),5, 18. Much focus will be on corn, tomatoes, with less on Arabidopsis , beans, brassicas, soyabeans, alfalfa and pine trees. On the economics of research see The Plant Cell 4: 619-20. Work on a genetic map of bean is described in Theor. Appl. Genetics 84: 186-92; and an analysis of genetic recombination in maize; Theor. Appl. Genetics 84: 65-72. Single tree genetic linkage mapping in conifers is reported in Biotechnology 10: 686-90. On the use of PCR in agriculture see GEN 12(9; 1992), 6-7. Transposon-tagging for genes is a promising way to isolate new genes; Biotechnology 10: 851-2. The alteration of male sterility in plant breeding is discussed in NS (18 July), 20.
Fertile transgenic wheat have been made, resistant to Basta herbicide; V. Vasel et al., "Herbicide resistant fertile transgenic wheat plants obtained by microprojectile bombardment of regenerable embryogenic callus", Biotechnology 10: 667-74, 630; NS (27 June), 19. To transform wheat is a major breakthrough, a major crop that had not been genetically transformed and regenerated in fertile progeny. Another recent crop to be genetically engineered is tall fescue; Biotechnology 10: 691-6.
An easy to read review of transgenic crops by C.S. Gasser & R.T. Fraley is in SA (June), 34-9, listing 40 crops that have already been genetically transformed. See the later section on safety of recombinant products for discussion of when we will eat them.
The problems of resistance to Bt is discussed in GEN 12(3), 1, 16. The corn borer resistance genes of corn have been mapped; GEN 12(7; 1992), 9. The relevant sections are being incorporated into new corn varieties by Ciba-Geigy and AgriGenetics. The field trials appear successful; NS (18 July 1992), 21. Research on plant disease resistance is described in Science 257: 482-3.
Resistance to bacterial disease is also a target, J.M. de la Fuente-Martinez et al., "Expression of a bacterial phaseolotoxin-resistant ornithyl transcarbamylase in transgenic tobacco confers resistance to Pseudomonas syringae pv. phaseolicola ", Biotechnology 10: 905-9. Potatoes resistant to Potato Virus X Infection have been made by expression of portions of the virus genome other than the coat protein genes; The Plant Cell 4: 735-44. Resistance to pea early browning virus is reported in PNAS 89: 5829-33.
It pays to be observant of species around us. Recent molecular studies of a moss which survives desiccation have lead to research on proteins that may confer its recovery ability, that could be transferred to crops; Science 257: 322. Star moss, Tortula ruralis , can recover from desiccation completely within 8-10 hours. So far 74 proteins that may be associated with this recovery ability have been found, which are being studied as proteins with potential for recovery of desiccation damage that are transferable to crops.
An example of metabolic engineering is T.A. Voelker et al., "Fatty acid biosynthesis redirected to medium chains in transgenic plants", Science 257: 72-4. They directed the synthesis of laurate in rapeseed. A different alteration in fatty acids is described in W.S. Grayburn et al., "Fatty acid alteration by a delta-9 desaturase in transgenic tobacco tissue", Biotechnology 10: 675-8. The use of biofuels is debated in Biotechnology 10: 630-1, and the future of plants in biotechnology in p.605.
The synthesis of antibodies in plants has been possible for several years, a further example is M. Owen et al., "Synthesis of a functional anti-phytochrome single-chain Fv protein in transgenic tobacco", Biotechnology 10: 790-4. The protein could be isolated by a single step of affinity chromatography.

The development of plants with broader temperature range tolerance is discussed in GEN (15 Sept 1992), 13, 23. Some believe that every plant has a preset thermostat for optimal growth, so by genetic engineering they aim to alter the optimal temperature for plants so that they can grow better at the different temperatures. It is also very important for the future when the climate will be warmer. Researchers recently transferred a gene from cucumbers to tobacco, to widen the temperature tolerance of the tobacco plant, as a model. The gene was for a "warm" optimal-working version of the enzyme, hydroxypyruvate reductase, involved in protecting plants from heat stress. More genes need to be identified to make the plant function properly at different temperatures. Further research on breeding cold-resistant wheat for Canada is reported in Science 257: 1347.
It is possible to produce large quantities of animal vaccines in plants , as shown by the UK company Agricultural Genetics; GEN (1 Sept), 1, 15. They use cowpea mosaic virus as a vector for antigens from animal viruses, the virus does not infect animals so there is no danger of reversion to infectious viruses.
The production of plastics , based on polyhydroxybutyrate (PHB), in plants is discussed in GEN (15 Sept 1992), 1, 19. These biodegradable plastics have already be made by bacteria, but cost about US$12-14 per pound; see EEIN 2: 46. The scientist developing it is concerned that if plastics are made in cash crop plants, the price of food may increase. Another team is working on combining this PHB with wood fibres to make a biodegradable material, 'fibrewood'; Science 257: 1479-80. Research on developing plants to clean-up the environment is described in Science 257: 1348.
In Japan the STA Research Development Corporation is commercialising plastics based on the polysaccharide chitosan, made from chitin (a shell component of insects, lobsters and crabs), cellulose, and starch; STA Today (Sept 1992), 9. In October a test began in Reading, England, on the feasibility of running buses on oil from oilseed rape - bioenergy ; NS (3 Oct 1992), 18. The use of trees as fuel in Africa, and the pollution problems that it leads to is reviewed in NS (29 Sept 1992), 35-9. New faster growing trees for bioenergy are an urgent need if larger areas are not to be converted into desert.
A study on what happens to the product of the coat protein gene of potato virus Y when transgenic virus resistant potatoes with the coat protein gene are infected with the potato virus is L. Farinelli et al., "Heterologous encapsidation of potato virus Y strain O (PVYO) with the transgenic coat protein of PVY strain N (PVYN) in Solanum tuberosum CV. Bintje", Bio 10: 1020-5. The coat protein is not detectable in normal healthy transgenic potato plants, but accumulated in infected plants, infected by a different virus strain.
An RNA-mediated virus protection in transgenic tomatoes is described in P. de Haan et al., "Characterization of RNA-mediated resistance to tomato spotted wilt virus in transgenic tobacco plants", Biotechnology 10: 1133-7. Another strategy for virus resistance is based on altering the enzyme replicase, required for growth of RNA viruses, see J.M. Anderson et al., "A defective replicase gene induces resistance to cucumber mosaic virus in transgenic tobacco plants", PNAS 89: 8759-63. They suggest that the approach may also be applicable for resistance to animal viruses.
A paper describing the method of broad spectrum resistance to Bacillus thuringiensis toxin (Bt) in an insect is F. Gould et al., "Broad-spectrum resistance to Bacillus thuringiensis toxins in Heliothis virescens ", PNAS 89: 7986-90. This should be of concern to all those developing Bt-resistant crop plants. Methods for testing for synergism among Bt toxins are described in AEM 58: 3343-6.
Norwegian Spruce trees have been genetically transformed by microprojectile bombardment; Plant Molecular Biology 19: 925-35. Some forest trees have been transformed by Agrobacterium -based vectors but none has been reportedly produced transgenic trees, so this new approach may make this goal achievable. Alteration of flower structure is possible by genetic manipulation, as described in M.A. Mandel et al., "Manipulation of flower structure in transgenic tobacco", Cell 71: 133-43.
The detection of DNA sequence polymorphisms in wheat varieties is reported in Theor. & Appl. Genetics 84: 573-8; while suitable genetic markers for wheat cultivar identification are reported in Theor. & Appl. Genetics 84: 535-43, 567-72. A composite RFLP linkage map of Brassica oleracea is reported in Theor. & Appl. Genetics 84: 544-54. A generalised gene tagging system for higher plants using an engineered maize transposon is described in Plant Molecular Biology 20: 177-98.
An interesting system for biological control that corn appear to use naturally is described in T.C.J. Turlings & J.H. Tumlinson, "Systemic release of chemical signals by herbivore-injured corn", PNAS 89: 8339-402. After being eaten corn release large amounts of terpenoids, which attract wasps, and the parasitic wasps should attack the herbivores. A review of the sense systems of plants is in NS (17 Oct 1992), 29-33. A review of the plant pest resistance signalling system is A.J. Enyedi et al., "Signal molecules in systemic plant resistance to pathogens and pests", Cell 70: 879-86. A journal review of two new journals, Biological Control and Biocontrol Science and Technology are in Nature 359: 450-1. On the use of nematodes in biological control see SA (Sept 1992), 121; and on home pest control and new technology see Pest Control (Sept 1992), 2a-7a.

A single gene that apparently regulates dormancy in plants has been found in studies in fruit trees; GEN (15 Oct 1992),12. It may be possible to alter the cold tolerance of plants by altering the level of expression and regulation of this gene. The transfer of a dominant powdery mildew resistance gene into cultivated barley from a wild relative is reported in Theor. Appl. Genetics 84: 771-7. The cloning of a gene controlling fatty acid desaturation in plants is in Science 258: 1353-5.
The results of glass house trials showing resistance to rice stripe virus by two japonica varieties of rice in a Japanese study are in PNAS 89: 9865-9. The rice plants expressing the coat protein gene are being field tested in 1993. Also in Japan, a new variety of self-pollinating Nashi (Asian pear) has been reported; Yomiuri Shinbun (12 Nov). On virus-resistant Papaya see Biotechnology 10: 1466-72. A review of emerging strategies to enhance crop resistance to microbial pathogens is in Biotechnology 10: 1436-45. Herbicide-tolerant Indica rice plants are reported in Plant Molecular Biology 20: 619-29.
A simple spray with 1ml of 10-50% methanol may increase the yield of crop plants using C3 photosynthesis when grown in arid conditions under direct sunlight for weeks; PNAS 89: 9794-8. The effect was much greater than nutrient effects, suggesting this may be a simple method for general use in desert agriculture. Try it! The possible strategies to genetically engineer Rubisco are reviewed in Aust. J. Botany 40: 421-9, 430-41.

The genome mapping of several plant species is underway. The order of gene markers on chromosomes of rice and maize has been found to be very similar, suggesting the gene order is conserved. This should make the mapping of different plant species progress faster; GEN (Dec 1992), 1, 3, 37. Wheat and barley, and maize and sorghum, have also been found to be related. Most wheat genome markers are found in humans, but the two genomes are structured somewhat differently. A review of gene studies is M.T. Clegg, "Chloroplast gene sequences and the study of plant evolution", PNAS 90: 363-7. A genome database for Arabidopsis called AAtDB is available from Sam Cartinhour, FAX Int+1-617-726-6893. On gene research to study plant development in Arabidopsis see Science 258 (1992), 1580-1.
A review of plant genetic engineering for disease resistance is in NS (9 Jan), 36-40. The prospects for virus resistance using antisense RNA are reviewed in TIBTECH 10 (1992), 383-8. More yield and fruit was reported from transgenic cucumbers expressing coat protein genes to cucumber mosaic virus compared with non-transformed resistant plants; Biotechnology 10 (1992), 1562-70. A report of fungal disease resistance induced by introduction of a gene for a phytoalexin is in Nature 361: 153-6.
A salt tolerant plant is reported in M.C. Tarczynski et al., "Stress protection of transgenic tobacco by production of the osmolyte mannitol", Science 259: 508-10. A naturally occuring plant, Salicornia begelovii is being farmed for cooking oil and protein feed for animals in Saudi Arabia and is being irrigated with sea water; Science 258 (1992), 1574. Fertile transgenic oats have been reported in Biotechnology 10 (1992), 1589-94. Transformation of white spruce, Picea glauca , is Biotechnology 11: 84-9. Regeneration of rice from mesophyll protoplasts is reported in Biotechnology 11: 90-4.
A review on the use of plant cell culture techniques to provide a reservoir for drugs and rare plants is in GEN (Dec 92), 12-3, 36. The use of cell culture to produce the anticancer drug taxol is reported in Biotechnology 10 (1992), 1572-5. It has been reported that a Himalayan relative of the Pacific Yew tree is another source of taxol. Concerns have been voiced about the survival of the Yew tree because it is used to produce taxol. Metabolic engineering of plants can produce useful products also, D.-J. Yun et al., "Metabolic engineering of medicinal plants: Transgenic Atropa belladonna with an improved alkaloid composition", PNAS 89 (1992), 11799-803. On the production of the polymer polyhydroxybutyrate in microbes and plants see Nature 360 (1992), 535. An example of engineering of a fatty acid desaturase enzyme in tobacco to produce unusual fatty acids is in PNAS 89 (1992), 11184-8.
A new Bacillus thuringiensis (Bt) toxin against ants is being developed for commercial use in the USA by Mycogen and collaborating companies; GEN (Jan), 17. Specific Bt toxins may be isolated for many different insects. Methods to manage the use of Bt toxins in agriculture are reviewed in W.H. McGaughey & M.E. Whalon, "Managing insect resistance to Bacillus thuringiensis toxins", Science 258 (1992), 1451-5. A review of the method of the insecticidal action of Bt is in BioScience 42 (1992), 112-22. Maize plants expressing a Bt protein performed well in field tests; Biotechnology 11: 194-200. The estimated cost of US pesticide use every year is about US$8 billion (double to market price); BioScience 42 (1992), 750-60.
Mutagenic techniques have been used by Montana State University scientists to develop self-destructing bioherbicides; GEN (15 Jan 1993), 1, 21. They used the fungus Sclerotinia scleroiorum , and one approach is to make the fungus auxotrophic requiring a substance found only in the weed to be destroyed. The fungus grows best under conditions of high humidity so one of the first products expected is for home lawns which can be watered regularly. On the opposite issue, making fungal resistant plants, the USDA has made new varieties of Elm tree resistant to Dutch Elm disease; GEN (15 Jan 1993), 15, 21. These were developed after about ten years of breeding, using crosses with Elms in Japan and China which had developed resistance to Dutch Elm disease (which has been in Asia longer than elsewhere).
The crystal structure of nitrogenase enzyme from Azotobacter vinelandii at 2.7A resolution has been published; Nature 360 (1992), 532-3, 553-60. This will aid the understanding of nitrogen fixation, and important long term goal of plant genetic engineering.

A single gene has been transferred to transgenic Barley that controls several traits, including height, maturity, drought resistance and strength; GEN (1 Mar 1993), 1, 22. The transgenic plants flower when less than half the height of control plants. It had been thought that diverse traits would not be controlled by a single gene, however, these experiments at Washington University in St. Louis, USA, show that this single gene can cause a range of affects. A review of plant biotechnology over the last decade is in Biotechnology 11 (March 1993): S22-26. Research aimed at improving Kenyan sweet potatoes by genetic engineering is reviewed in GEN (1 April 1993), 1, 25.
Edible plastic suitable for animal food has been developed in Iowa State University in the USA; GEN (1 Mar), 32. The plastic is derived from vegetable material such as corn or soybeans, and dissolves slowly in water. Research on improved canola, vegetable oil, for humans has resulted in hybrid seed and genetic research aimed at improving its already good properties; Biotechnology 11: 448-9. A review of food engineering is R.G.F. Visser & E. Jacobsen, "Towards modifying plants for altered starch content and composition", TIBTECH 11: 63-8.
There is increasing use of somatic embryogenesis in forestry , and it is expected to further increase; Biotechnology 11: 454-8. A discussion of the issues in tropical forests is in Ambio 22: 50-1. A paper reporting the use of antisense chalcone synthase genes to alter flower pigments in Gerbera hybrida is Biotechnology 11: 508-11.
PCR can be used to analyse the DNA from single protoplasts of regenerated plants, for checks of gene transfer and polymorphism; Molecular & General Genetics 237: 311-7. The use of antisense RNA to restore fertility to engineered male sterile tobacco is reported in Molecular & General Genetics 237: 385-94. A book review of Plant Resistance to Herbivores and Pathogens is Science 259: 1631-2; and of World Medicine: Plants, Patients and People ; Nature 362: 27-8. One herbicide resistance gene that has been identified is a nitrate-inducible nitrate transporter protein; Cell 72: 705-13. Studies on the use of Bacillus thuringiensis as an insecticide include AEM 59: 523-7, 815-21.
The production of the anticancer substance, taxol in a fungi is reported in Science 260: 154-5, 214. A fungal pathogen, Colletotrichan magna was genetically converted to a nonpathogenic endophytic mutualist by a single gene change; Science 260: 75-8.

Baculovirus expression systems are being commercially applied in research and industry; GEN (15 March),10-11. They have advantages over E. coli and animal cell culture protein systems.
The use of the aux2 gene of Agrobacterium rhizogenes as a conditional negative marker in transgenic cabbage is suggested in Transgenic Research 2: 48-55. Two new markers for plant selection include bacterial dihydrodipicolinate synthase and desensitized aspartate kinase, Biotechnology 11: 715-8. A copper controllable gene expression system based on the yeast metallothionein gene is reported in PNAS 90: 4567-71.
The transformation of cotton cultivars by particle bombardment is reported in Biotechnology 11: 596-8. The bacterial virulence gene virF can be transferred to plants to convert the plants into hosts for Agrobacterium ; Nature 363: 69-71. The use of Agrobacterium for gene transfer in maize is reviewed in PNAS 90: 3119-20.
Several new species with transposons have been identified which raises possibility of applications. Transposons have been used in maize for gene tagging; Nature 363: 669-70. Mobile transposons in Arabidopsis thaliana have been identified, Science 260: 342-4; and used to tag a male sterility gene, Nature 363: 715-7. The induction of male sterility in tobacco by an unedited atp9 wheat mitochondrial gene suggests that male sterility is caused by dysfunction of mitochondria; PNAS 90: 2370-4.
A database on Arabidopsis thaliana has been released by the USDA and Massachusetts General Hospital. A review of molecular analysis of the small grain cereals is in Biotechnology 11: 584-9. They suggest a composite map of the ancient grass genome .
A review is T.M.A. Wilsonm, "Strategies to protect crop plants against viruses: Pathogen-derived resistance blossoms", PNAS 90: 3134-41. The use of antisense approaches to provide plant viral resistance is being effectively pursused by the USDA; GEN (15 Feb 1993), 11. The experiments have used tobacco, and include protection against bean yellow mosaic virus, and potyviruses in general. In other research at the USDA, genes that protect citrus trees against citrus tristeza virus (carried by brown citrus aphid), have been identified; GEN (15 March 1993),14. In Florida alone about 18% of the grapefruit trees are susceptable to the virus. A detection test for plum pox virus has also been developed; GEN (1 Jun 1993), 11, 32. A TMV strain capable of overcoming N Gene-mediated resistance is analysed in Plant Cell 5: 577-86.
Popular trees (a fast growing tree, useful as fuel) have been made resistant to both lepidopterans and coleopterans using Bacillus thuringiensis (Bt) insecticidal protein genes; GEN (15 March 1993), 25. Screening of Bt genes are described in AEM 59: 1683-7; and resistance to Bt in Diamondback moth is studied in AEM 59: 1332-5. They report the development of some cross-resistance by exposure to one subspecies Bt protein for another Bt protein. The toxicity of baculoviruses towards insects can be increased by expression of a maize mitochondrial protein URF13; PNAS 90: 3388-92. A gene that protects peas from a fungal disease, Verticillium wilt has been transfered, along with resistance, to potatoes; GEN (1 Jun 1993), 14.
The use of plant tissue culture of Taxus spp. to produce taxol in vitro can be made more efficient by modifying the medium to include phenylalanine; Biotechnology 11: 731-4. A fungus Taxomyces andreanae has been found that also produces taxol, a chemical shown to combat breast and ovarian cancer; Science ; Newsweek (19 April 1993), 55. In general biotechnology has yet to provide what researchers have promised in agriculture but products are expected soon; U.S. News & World Report (3 May 1993), 67-8. A letter on the chemical properties of the biopolymer poly-R-3-hydroxybutyrate is in Nature 363: 23. Although when isolated it is a crystal, in cells it is stored as a mobile elastic protein.

The development of edible cholera vaccine in alfalfa is being tested by the Scripps Institute and Samuel Roberts Nobel Foundation in the USA; GEN (15 June), 1, 19. They also describe the other groups in the USA researching edible vaccines, which includes use of bananas, as discussed previously in the EEIN 3: 2.
After many attempts, plant gametes have been joined in test tubes; Science 261: 430-1; The Plant Cell (July). Corn gametes were joined by a brief pulse of electricity. A paper on "dry" pollen and the gene mutation behind nonsticky pollen is in Nature 364: 573-4; Genes & Development 7: 974-85.
A review of progress in food biotechnology and genetic engineering of plants is Biotechnology 11: 895-901. Commercial interest centres on pest resistance, herbicide tolerance and food quality. An EPA report has concluded that herbicide-resistant crops have the potential to reduce pollution; Biotechnology 11: 783-4. The use of the genetic engineering to make the enzyme phytase in tobacco seeds which are given to chickens to improve phosphate metabolism is reported in J. Pen et al., "Phytase-containing transgenic seeds as a novel feed additive for improved phosphorus utilization", Biotechnology 11: 811-4.
One way to overcome difficulties of introducing foreign genes into cereals is expressing the genes in an endophytic fungus that lives within the desired plant; Agricell Report 19 (Nov 1992), 33-4. New Zeal;and researchers used this novel approach for introducing GUS marker genes into protoplasts of the endophyte Acremonium of perennial ryegrass (Lolium perenne ). A new TMV vector has been used for gene transfer to tomato and tobacco; Biotechnology 11: 930-2. The technique of genetic subtraction (inhibiting gene expression) is being used by some companies, such as DNAP; Biotechnology 11: 874.
Two US companies, Agracetus and Calgene are attempting to develop genetically engineered blue cotton , to avoid using the chemical blue dyes for making blue jeans; NS (31 July), 7.
On plastid transformation, TIBTECH 11: 101-7. On rice resistant to sheath blight pathogen; Biotechnology 11: 835-9. A review of the genes involved in nitrogen fixation and Rhizobium symbiosis is Science 260: 1764-5.
On biopesticides see Science 261: 277. Salicyclic acid is required for induction of systemic acquired resistance in tobacco; Science 261: 754-6.

The genome sizes of plants range greatly, and a report on current genome studies is in Nature 365: 297-8. The studies allow comparisons of gene order and recombination frequency, which vary widely. Large genomes, like wheat, recombine less than small ones, explaining why they may be so long. The implications of conserved genome structure in plants are discussed in PNAS 90 8303-9. Comparative linkage maps of rice and maize are published in PNAS 90: 7980-4.
The expression of a rat antiviral gene, 2'-5'- oligoadenylate synthetase in potatoes protected them from Virus X in field studies; Biotechnology 11: 1048-52. This is interesting for not only agriculture, but also for studies of antiviral mechanisms of cells. Potyvirus resistance using transfer of a cistron of potato virus Y protease are reported in PNAS 90: 7513-7. A review of the ecological safety of viral resistance, and the likely effects viral resistant plants will have on the virus populations is Biotechnology 11: 1125-32. It also discusses viral recombination.
A paper reporting insect-resistant rice is H. Fujimoto et al.,, "Insect resistant rice generated by introduction of a modified d-endotoxin gene of Bacillus thuringiensis ", Biotechnology 11: 1151-5. A paper reporting altered homeobox gene alters plant morphology is Plant Cell 5: 1039-48.
A letter commenting on the published field studies of herbicide-tolerant transgenic rape is Nature 365: 114. A new study on the future prospects for the Green revolution continuing to increase food yield is reviewed in Science 261: 1517. It notes that Indonesia is continuing to increase rice yield, (also it does not use pesticides).

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