FUNGAL AND PLANT GENE-EXPRESSION DURING SYNCHRONIZED INFECTION OF TOMATO LEAVES BY BOTRYTIS-CINEREA

An inoculation procedure was developed to obtain efficient and synchro nous infection on detached tomato leaves by Botrytis cinerea. In spray -inoculated leaves incubated at 20 degrees C, the infection process co nsisted of three phases: the formation of primary necrotic lesions (un til 20 hpi), a quiescent phase (20-72 hpi), and the expansion of a pro portion of the primary lesions (from 72 hpi onwards), resulting in ful l tissue maceration. At 4 degrees C, the infection progressed slowly b ut steadily without inducing necrotic responses in the host. The actin and beta-tubulin genes of B. cinerea were cloned, characterized and u sed as probes on blots containing RNAs from leaves at various stages o f the infection. The genes displayed a similar expression pattern thro ughout the infection and the hybridization signal reflected the amount of fungal biomass. The actin mRNA accumulated to higher levels than t he beta-tubulin mRNA. Tomato PR protein mRNAs (chitinase, beta-1,3-glu canase and PR-1) were induced during the infection, albeit with differ ent kinetics and to different levels. At 20 degrees C, beta-1,3-glucan ase and PR-1 mRNAs were induced more rapidly than chitinase mRNAs. At 4 degrees C, mRNAs encoding extracellular beta-1,3-glucanase and intra cellular, as well as extracellular chitinase were hardly induced.