EVIDENCE FOR TRANSCRIPTIONAL REGULATION OF BETA-1,3-GLUCANASE AS IT RELATES TO INDUCED SYSTEMIC RESISTANCE OF TOBACCO TO BLUE MOLD

The hybridization signal for beta-1,3-glucanase (PR-N) mRNA was detected in the lower inoculated leaves and upper uninfected leaves of N-gene tobacco plants 3 and 12 days, respectively, after inoculation of lower leaves with tobacco mosaic virus (TMV). The signal markedly increased 1 to 2 days after challenge of upper leaves with Peronospora tabacina, whereas only a slight increase was apparent 3 to 4 days after mock challenge. The signal was not apparent in mock challenged upper leaves, but it was detected 4 days after challenge in upper leaves of plants mock inoculated with TMV. Plants inoculated with TMV were highly protected against P. tabacina. These results indicate a positive association of PR-N mRNA with induced resistance to P. tabacina and the apparent sensitization of the induced plants to rapidly produce PR-N mRNA after challenge with P. tabacina.