ENHANCED PROTECTION AGAINST FUNGAL ATTACK BY CONSTITUTIVE COEXPRESSION OF CHITINASE AND GLUCANASE GENES IN TRANSGENIC TOBACCO

Plants respond to pathogen attack by the induction of a battery of def enses, suggesting that different protective mechanisms may have comple mentary roles in the overall expression of disease resistance. We have investigated possible functional interactions between two different h ydrolytic enzymes, chitinase and glucanase, by constitutive co-express ion in transgenic tobacco of genes encoding the rice RCH10 basic chiti nase and the alfalfa AGLU1 acidic glucanase. Hybrid plants were genera ted by crossing transgenic parental lines exhibiting strong constituti ve expression of cauliflower mosaic virus (CaMV) 35S enhancer / RCH10 and CaMV 35S double promoter / AGLU1 gene fusions, respectively. Evalu ation of disease development in these hybrids, heterozygous for each t ransgene, and in homozygous selfed progeny, showed that combination of the two transgenes gave substantially greater protection against the fungal pathogen Cercospora nicotianae, causal agent of frogeye, than e ither transgene alone. Productive interactions between chitinase and g lucanase transgenes in vivo point to combinatorial expression of antim icrobial genes as an effective approach to engineering enhanced crop p rotection against fungal disease.