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The production of enzymes capable of degrading the cell walls of invading phytopathogenic fungi is an important component of the defense response of plants. The timing of this natural host defense mechanism was modified to produce fungal-resistant plants. Transgenic tobacco seedlings constitutively expressing a bean chitinase gene under control of the cauliflower mosaic virus 35S promoter showed an increased ability to survive in soil infested with the fungal pathogen Rhizoctonia solani and delayed development of disease symptoms.

Over the past three decades, there has been increasing consumer awareness of the health issues related to diet. Of all the nutrients in the modern diet, none has caused more concern to both consumers and nutritionists than dietary fat (Wiseman, 1992). This concern has arisen from the association between certain types of fat in the diet and a number of human diseases, especially cardiovascular disease.

The enzyme acetolactate synthase (ALS) is the target of several classes of herbicides, including the sulfonylureas, the imidazolinones, and the triazolopyrimidines. ALS is required for the biosynthesis of isoleucine, leucine and valine. We have cloned ALS genes from a variety of monocotyledonous and dicotyledonous plants. The number of ALS genes in these species varies from one, as in Arabidopsis and sugar beets, to two or more, as in corn and soybeans. The deduced amino acid sequences of the mature plant ALS genes which have been sequenced are closely related. Three domains of the plant ALS proteins are also conserved relative to bacterial and yeast ALS proteins. ALS genes have been isolated and sequenced from sulfonylurea herbicide resistant plants and the resistance trait shown to result from single or double mutations in the conserved domains of the genes. To produce additional genes able to confer sulfonylurea herbicide resistance in transgenic crops, in vitro-generated mutations were introduced into the coding regions of cloned plant ALS genes. A number of single and double mutations were shown to be effective in conferring resistance, upon subsequent introduction of the altered genes into plants. The mutations conferred varying degrees of resistance, depending upon the site of the resulting amino acid substitution and upon the amino acid substituted at that site. Replacement of ALS regulatory sequences led to increases in the proportion of herbicide resistant enzyme such that up to 90% of the total ALS activity was herbicide resistant. The altered genes conferred sulfonylurea herbicide resistance in glasshouse trials of a wide variety of transgenic crop species. Additionally, transgenic tobacco, tomato and oilseed rape were shown to be herbicide resistant in field trials.

Infection of Alnus rubra Bong, roots by Frankia isolates was consistently promoted by Pseudomonas cepacia "helper" bacteria under a variety of cultural conditions. Pseudomonas cepacia, while helpful, was never necessary in securing nodulation of aseptic A. rubra by Frankia. Live P. cepacia cells were added with a Frankia isolate to aseptically grown A. rubra seedlings on Hoagland's agar slants. This doubled, on average, the number of nodules formed by Frankia alone when Frankia isolate, age of Frankia inoculum, Frankia medium, calcium concentration of seedling substrate, phosphate concentration of seedling substrate, and pH of seedling substrate were varied. There was an apparent interaction between seedling substrate pH and P. cepacia in the promotion of nodulation. At pH levels from 4.0 to 6.0 the infectivity of Frankia isolate ArI3 alone was greatly depressed compared with infectivity at the optimal pH for the growth of ArI3, around 7.0. However, at pH levels of 5.0, 5.5, and 6.0 the ability of P. cepacia to promote nodulation of A. rubra seedlings by ArI3 was greater than at pH 7.0. This interaction may be due to the ability of P. cepacia to neutralize and grow more rapidly in mildly acidic solutions in our experimental system, combined with the ability of P. cepacia to cause root-hair deformation, which has been associated with the actinorhizal infection process.

Nodulation of actinorhizal plants (Alnus rubra Bong. and others) by isolated Frankia strains occurred either at a low frequency or not at all under axenic conditions. But nodulation was achieved under nonsterile conditions and four strains of bacteria were isolated which promoted nodulation when plants were inoculated with the bacteria plus Frankia. Four strains of Psendomonas cepacia also promoted nodulation. Root hair deformation occurred when roots of A. rubra were inoculated with these bacterial isolates, or with the bacteria plus Frankia, but rarely or not at all when roots were inoculated with the actinomycete alone. The nonendophytic bacterial strains were not detected within the nodule tissue. It is proposed that the bacterial isolates aid in the infection process at the host root hair surface, by causing root hair deformation; this may allow intimate contact between the Frankia filament and the hair wall.

A procedure was developed for the formation and regeneration of protoplasts in Clostridium tertium . Although in the parent strain most of the protoplasts gave rise to L-form colonies, derivatives could be isolated which exhibited high regeneration frequencies.