Down-regulation of defense gene transcripts of Rhizoctonia solani-infected bean seedlings in response to inoculation with non-pathogenic fungi.

摘要

In this study, we have demonstrated that inoculation of bean seeds with non-pathogenic binucleate Rhizoctonia (np-BNR) at sowing protected bean seedlings from infection of R. solani. Using quantitative real-time RT-PCR (QRT-PCR), transcript levels of defense genes encoding 1,3-beta-glucanase (GLUC), phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS) in one-week old bean seedlings was monitored during np-BNR and R. solani interaction. The results revealed that protection effect of np-BNR correspond to a systemic suppression of these three defense genes' expression from significant higher level elicited by R. solani to the level of non-infected plants. This indicates that bio-protection by np-BNR isolates is not correlated to activation of these three defense genes' expression. Similar suppression was achieved for pre-colonization of bean seedlings with arbuscular mycorrhizal (AM) Glomus introradices on GLUC gene expression, although the AM fungus did not significantly reduce rot symptoms. Possible mechanisms implicated in down-regulation during plant-pathogen and np-BNR or AM interaction are discussed.