DIFFERENTIAL EXPRESSION AND INDUCTION OF CHITINASES AND BETA-1,3-GLUCANASES IN RESPONSE TO FUNGAL INFECTION DURING GERMINATION OF MAIZE SEEDS

Chitinases and beta-1,3-glucanases are believed to be important in defending plants against pathogens. Here, we examined the expression of beta-1,3-glucanases and chitinases in response to infection by the fungus Fusarium moniliforme during germination of maize seeds. Accumulation of both hydrolases in embryo and vegetative tissues of maize seedlings were analyzed. Immunoblotting and immunoprecipitation of total in vitro translated proteins using antibodies against the maize pathogenesis-related proteins characterized as beta-1,3-glucanases and chitinases were performed. We found a coordinated induction of the expression of one beta-1,3-glucanase and three chitinase isoforms in maize seedlings in response to infection by the fungus F. moniliforme. The observed induction of the expression of the beta-1,3-glucanase isoform correlates with an increase in the level of translatable mRNA for this particular isoform. In contrast, a second beta-1,3-glucanase isoform was also expressed in embryo and radicle tissues, but its level of accumulation was not increased upon fungal infection. These findings suggest that beta-1,3-glucanases, in addition to their possible role in the defense response against pathogens, may have a developmentally regulated expression and a role in the normal process of seed germination. The pattern of accumulation of the various beta-1,3-glucanase and chitinase isoforms and their responses to fungal infection in radicles and coleoptiles are distinct from those seen in embryo tissues of maize seedlings. These data indicate that in addition to tissue-specific expression, there is a differential pathogen regulation of the expression of the different beta-1,3-glucanases and chitinases during germination of maize seeds.