Host Gamma-Aminobutyric Acid Metabolic Pathway Is Involved in Resistance Against Rhizoctonia solani.

Abstract

Rhizoctonia solani is a highly destructive necrotrophic fungal pathogen having a diverse host range, including rice and tomato. Previously R. solani infection has been found to cause large-scale readjustment in host primary metabolism and accumulation of various stress-associated metabolites such as gamma-aminobutyric acid (GABA) in rice. In this study, we report upregulation of GABA pathway genes during pathogenesis of R. solani in rice and tomato. The exogenous application of GABA provided partial resistance against R. solani infection in both the hosts. Furthermore, by using the virus-induced gene silencing approach, we knocked down the expression of some of the tomato genes involved in GABA biosynthesis (glutamate decarboxylase) and GABA catabolism (GABA-transaminase and succinic semialdehyde dehydrogenase) to study their role in host defense against R. solani infection. The silencing of each of these genes increased disease susceptibility in tomato. Overall the results from gene expression analysis, exogenous chemical application, and gene silencing studies suggest that the GABA pathway plays a positive role in plant defense against necrotrophic pathogen R. solani.