iTRAQ-based proteomic analysis of defence responses triggered by the necrotrophic pathogen Rhizoctonia solani in cotton.

The soil-borne necrotrophic pathogen fungus Rhizoctonia solani is destructive, causing disease in various important crops. To date, little is known about the host defence mechanism in response to invasion of R. solani. Here, an iTRAQ-based proteomic analysis was employed to investigate pathogen-responsive proteins in the disease tolerant/resistant cotton cultivar CRI35. A total of 174 differentially accumulated proteins (DAPs) were identified after inoculation of cotton plants with R. solani. Functional categorization analysis indicated that these DAPs can be divided into 12 subclasses. Notably, a large portion of DAPs are known to function in reactive oxygen species (ROS) metabolism and the expression of several histone-modifying and DNA methylating proteins were significantly induced upon challenge with the fungus, indicating that the redox homeostasis and epigenetic regulation are important for cotton defence against the pathogen. Additionally, the expression of proteins involved in phenylpropanoid biosynthesis was markedly changed in response to pathogen invasion, which may reflect a particular contribution of secondary metabolism in protection against the fungal attack in cotton. Together, our results indicate that the defence response of cotton plants to R. solani infection is active and multifaceted and involves the induction of proteins from various innate immunity-related pathways. SIGNIFICANCE: Cotton damping-off is a destructive disease caused by the necrotrophic fungus Rhizoctonia solani. To date, the host defence mechanism involved in the disease protection remains largely unknown. Here, we reported the first proteomic analysis on cotton immune responses against R. solani infection. Employing iTRAQ technique, we obtained a total of 174 differentially accumulated proteins (DAPs) that can be classified into 12 functional groups. Further analysis indicated that ROS homeostasis, epigenetic regulation and phenylpropanoid biosynthesis were tightly associated with the innate immune responses against R. solani infection in cotton. The obtained data provide not only important information for understanding the molecular mechanism involved in plant-R. solani interaction but also application clues for genetic breeding of crops with improved R. solani resistance.