CF GENE-DEPENDENT INDUCTION OF A BETA-1,3-GLUCANASE PROMOTER IN TOMATO PLANTS INFECTED WITH CLADOSPORIUM-FULVUM

Tomato Cf genes confer resistance to specific races of the leaf mold pathogen Cladosporium fulvum. The Cf gene-dependent induction of a Nicotiana plumbaginifolia beta-1,3-glucanase (gn1) promoter -GUS reporter gene fusion was monitored following either inoculation with race 0 C. fulvum or leaf injections with race-specific elicitors. In incompatible interactions, intense foci of GUS activity appeared at infection sites 1-4 days after hyphae entered the leaf through stomata. The time of appearance of these foci and their relative final size was different on Cf-2, Cf-4, Cf-5, or Cf-9-containing near-isogenic lines (NILs) of the cultivar Moneymaker. In the compatible interaction, gn1:GUS induction was later and occurred just prior to sporulation. Co-localization of GUS activity and fungal hyphae revealed that the spatial patterns of induction in relation to fungal hyphae differed between the various incompatible interactions studied. Following race-specific elicitor injection, increased GUS activity was only detected in Cf gene-containing NILs. Induction was detected in the Cf-9 containing NIL within 12 hr and in those carrying Cf-2 or Cf-5 within 24 hr. RNA gel blot analysis showed that the induction kinetics of the gn1 promoter resembled that of an endogenous acidic beta-1,3-glucanase gene.