ABSTRACT
Unripe mature green fruits of pepper (Capsicum annuum) are susceptible to Colletotrichum gloeosporioides, whereas ripe red fruits are not. We established this pepper-C. gloeosporioides interaction as a model system to study the fungal resistance that develops during ripening of nonclimacteric fruit. Histochemical examination of transverse sections suggested that fungal invasion 24 h after inoculation (HAI) and colonization 48 HAI are critical events that differentiate between resistant and susceptible interactions. Based on this observation, we used messenger RNA differential display to isolate defense-related genes differentially expressed at 24 and 48 HAI. RNA gel blot analysis showed that six out of eighty cloned cDNAs were differentially expressed after infection of ripe fruit. The proteins encoded by these six clones, ddP1, ddP3, ddP4, ddP6, ddP13, and ddP47, showed significant homology to aldehyde dehydrogenase, P23 protein, NP24 protein, cytochrome P450 protein, esterase, and MADS-box protein, respectively, and may be involved in the resistance of ripe fruit to C. gloeosporioides infection.
