, an RNA-Dependent RNA Polymerase Plays a Positive Role in Pepper Resistance against TMV.

RNA silencing functions as a major natural antiviral defense mechanism in plants. RNA-dependent RNA polymerases (RDRs) that catalyze the synthesis of double-stranded RNAs, are considered as a fundamental element in RNA silencing pathways. In and play important roles in anti-viral RNA silencing. Expression of can be elevated following plant treatment with defense hormones and virus infection. has been studied in several crop species, but not in pepper ( L.). Here, a gene was isolated from L., designated as . The full-length cDNA of was 3,351 bp, encoding a 1,116-amino acid protein, which contains conserved regions, such as the most remarkable motif DLDGD. The transcripts of could be induced by salicylic acid (SA), abscisic acid (ABA), HO, and tobacco mosaic virus (TMV). Silencing of in pepper resulted in increased susceptibility to TMV as evident by severe symptom, increased of TMV- transcript, higher malondialdehyde (MDA) content and lower antioxidant enzymes activities compared with that of control plants. -overexpressing in showed mild disease symptom and reduced TMV- transcripts than that of empty vector (EV) following TMV inoculation. The RNA silencing related genes, including , and elevated expression in overexpressed plants. Alternative oxidase (AOX), the terminal oxidase of the cyanide (CN)-resistant alternative respiratory pathway, catalyze oxygen-dependent oxidation of ubiquinol in plants. It has an important function in plant defense against TMV. In addition, overexpression promoted the expression of and . In conclusion, these results suggest that plays a positive role in TMV resistance by regulating antioxidant enzymes activities and RNA silencing-related genes expression to suppress the replication and movement of TMV.