CHARACTERIZATION AND EXPRESSION OF CHITINASE AND 1,3-BETA-GLUCANASE GENES IN COTTON

We have isolated cDNA clones representing mRNAs encoding chitinase and 1,3-beta-glucanase in cotton (Gossypium hirsutum L.) leaves. The chit inase clones were sequenced and found to encode a 28,806 Da protein wi th 71% amino acid sequence similarity to the SK2 chitinase from potato (Solanum tuberosum). The 1,3-beta-glucanase clones encoded a 37,645 D a protein with 57.6% identity to a 1,3-beta-glucanase from soybean (Gl ycine max). Northern blot analyses showed that chitinase mRNA is induc ed in plants treated with ethaphon or salicylic acid, whereas the leve ls of 1,3-beta-glucanase mRNA are relatively unaffected. Southern blot s of cotton genomic DNA and genomic clones indicated chitinase is enco ded by a small gene family of which two members, Chi 2;1 and Chi 2;2, were characterized. These genes share 97% sequence identity in their t ranscribed regions. The genes were found to have three exons which are 309, 154 and 550 bp long, and two introns 99 and 154 bp in length. Th e 5'-flanking regions of Chi 2;1 and Chi 2;2 exhibit a large degree of similarity and may contain sequences important for gene response to c hemical agents and fungal attack.