MOLECULAR-CLONING AND INDUCTION OF BETA-1,3-GLUCANASE GENE FROM NICOTIANA-GLUTINOSA L

Cloning and characterization of disease-response genes in plants could be an initial step toward understanding the complex disease resistanc e mechanism. To better understand the complex step, we isolated one of the pathogenesis-related proteins, beta-1,3-glucanase, cDNA from a cD NA library of Nicotiana glutinosa showing systemic resistance. One clo ne (GN-3) was a partial cDNA of beta-1,3-glucanase 800 bp in size with a 171 amino acid coding region. This clone had a 90% nucleotide homol ogy with the beta-1,3-glucanase gene of N. tabacum cv. BY4. A deduced amino acid sequence of GN-3 clones indicated a 91% identity with the b eta-1,3-glucanase of tobacco, 58% with that of Lycopersicon esculentum , and 51% with that of Glycine max. Northern blot analysis showed that expression of beta-1,3-glucanase mRNAs was induced by TMV infection a nd salicylic acid treatment. In addition to that this gene was highly induced by CuSO4 and beta-aminobutyric acid which are known as inducer s of plant disease resistance. The possible role of this gene expressi on in relation to chemical-induced plant defense responses is discusse d.