Abstract

Role of Epigenetics and Tomato 26S Proteasome Subunit RPT4a in Providing Tolerance against Plant Viruses

Manoj Prasad, Staff Scientist VI, National Institute of Plant Genome Research

Tomato leaf curl disease (ToLCD), caused by strains of Tomato leaf curl virus (ToLCV), is a major constraint to tomato production. To understand the molecular mechanism of virus tolerance, we studied the abundance of viral genomic replicative intermediate molecules and virus-derived siRNAs by host plant in a naturally tolerant (H-88-78-1) and susceptible (Punjab Chhuhara) cultivars at different days-post-infection. We showed that less abundance of viral replicative intermediate in tolerant cultivar may have a correlation with a relatively higher accumulation of virus-specific siRNAs. Further, a significant correlation was observed between altered methylation patterns in tolerant versus susceptible cultivars. These suggest that both viral DNA methylation and siRNA-mediated degradation play an important role in conferring tolerance against ToLCNDV. Further, we functionally characterized a 26S proteasomal subunit RPT4a (SlRPT4) gene, which was differentially expressed after ToLCNDV infection in tolerant cultivar. The study showed that SlRPT4 protein binds to promoter region of ToLCNDV genome thereby hindering the expression of virus genes which subsequently reduces viral replication and infection in tolerant cultivar. Transient overexpression of SlRPT4 resulted in activation of programmed cell death and antioxidant enzymes system. Overall, present study highlights non-proteolytic function of SlRPT4 and their participation in defense-pathway against virus infection in tomato.