(physical and biological) are discussed with comparisons being made between insect and mammalian cells.

Commercialization of genetically engineered plants by Roy L. Fuchs and Frederick J. Perlak

OELLER PW, MEVWONG L, TAYLOR LP, PIKE DA, THEOL~GIS A Reversible Inhibition of Tomato Fruit Senescence by Antisense RNA Science 1991, 254437439. Antisense RNA was used to effectively inhibit ethylene production in tomato, and an inhibition of ripening was observed. This demonstrates that ethylene is the trigger of ripening and not a by-product.

KIEE HJ, HAYFORD MB, KRETZMER KA, BARRY GF, KISHORE -GM: Control of Ethylene Synthesis by Expression of a Bacterial Enzyme in Transgenic Tomato Plants. Plant Cell 1991, 3:1187-1193. A gene for a bacterial l-aminocyclopropane-l-carboxy- late deaminase was introduced into tomato plants and successfully inhibited. fruit ripening via a reduction of ethylene synthesis. The quality of the resulting fruit offers immediate commercial opportunities.

IJ J, CARROLL J, ELLAR DJ: Crystal structure of Insectidal Delta-endotoxin from Bacillus thuringiensis at 2.5 A Resolution. Nature l991 3538154321. The first crystal structure of a Bacillus thuringiensis insect-control protein is described and may help to de- termine the mode of :action of all insect-control proteins from Bacillus thuringiensis.

Plant responses to environmental stress by Elizabeth Vierling and Janice A. Kimpel

TARCZYNSKI MC, JENSIEN RC, BOHNERT HJ: Expression of a Bacterial mtlD Gene in Transgenic Tobacco Leads to Production and Accumulation of Mannitol. Proc Nat1 Acad Sci ZJSA 1992, 8932600-2604. The first example of increasing osmolyte produc- tion by genetic engineering. An enzyme responsible for mannitol catabolism causes mannitol accumulation in transgenic tobacco. Tobacco does not normally accumulate mannitol so a new metabolic pathway has been introduced.

FIAHERTY KM, McK.w DB, KABSCH W, HOLMES KC: Similarity of the Three-dimensional Structures of Actin and the ATPase Fragment of a 70kDa Heat Shock Cognate Protein. Proc Nat1 Acad Sci USA 1991, 88:5041-5045. X-ray crystal structure data showing that the amino- terminal half of HSP70 is structurally similar to actin. Continued progress in structural analysis of HSP70 is

essential for defining the mechanism of molecular chaperone action.

PEARCE G, STR~D~M D, JOHNSON S, RYAN CA A Polypeptide From Tomato Leaves Induces Wound- inducible Proteinase Inhibitor Proteins. Science 1991, 253:895-898. A landmark paper that introduces a class of hormonal molecules never previously described for plants.

Development of tagging systems in plants using heterologous transposons by Anuj M. Bhatt and Caroline Dean

MA.SSON P, STREM M, FEDOROFF N: The tnpA and tnpD Gene Products of the Spm Element are Required for Transposition in Tobacco. Plant Cell 1991, 3:73%35. Complementary DNAs encoding four alternatively spliced transcripts of Spm were analyzed in different combi- nations for their ability to transactivate excision of a &pm element in tobacco. The structure of empty donor sites, dSpm insertion sites. and potential transposition intermediates are discussed.

DOONER H, KELLER J, HARPER E, RALSTON E: Variable Patterns of Transposition of the Maize Element Ac- tivator in Tobacco. Plant Cell 1991, 3:473482. The pattern of AC transposition in tobacco was assayed. Transposed AC elements were mapped relative to the donor SPT gene. There was locus-to-locus variation in the distribution of transposed AC elements. The results have implications for the success of targeted tagging strategies in tobacco.

OSBORNE BI, CORR CA, PRINCE JP, HEHL R, TANKSLFZY SD, MCCORMICK S, BAKER B: AC Transposition from a T-DNA can Generate Linked and Unlinked Clusters of Insertions in the Tomato Genome. Genetics 1991, 129:8334344. The distribution of transposed AC elements in the tomato genome was analysed. Sequences flanking the T-DNA and transposed elements were cloned from genomic libraries or by inverse polymerase chain reaction and placed on the tomato RPLP map. AC was transposed to linked and unlinked sites in the tomato.

BELZILE F, YODER JI: Pattern of Somatic Transposi- tion in a High Copy AC Tomato Line. Plant J 1992, 2:173-179.

A transgenic tomato line containing an exceptionally ac- tive AC element was used to clone 24 independent AC in- sertion events The chromosomal location of 20 AC in- sertion sites on the tomato RFLP map was determined. Only one AC insertion was linked to the T-DNA, while most other AC insertions were mapped as clusters of two to five linked elements to eight different chromosomes.

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