N-Methyltransferase Acts as a Positive Regulator of Immunity against Bacterial Pathogens in Pepper.

Proteins with conserved SET domain play a critical role in plant immunity. However, the means of organization and functions of these proteins are unclear, particularly in non-model plants such as pepper ( L.). Herein, we functionally characterized , a member of class II (the ASH1 homologs H3K36) proteins in pepper immunity against and pv DC3000 ( DC3000). The was localized in the nucleus, and its transcript levels were significantly enhanced by inoculation (RSI) and exogenous application of salicylic acid (SA), methyl jasmonate (MeJA), ethephon (ETH), and abscisic acid (ABA). Knockdown of by virus-induced gene silencing (VIGS) compromised peppers' resistance to RSI. Furthermore, silencing of impaired hypersensitive-response (HR)-like cell death response due to RSI and downregulated defense-associated marker genes, including , , and The protein was revealed to affect the promoters of , , and Transiently over-expression of in pepper leaves elicited HR-like cell death and upregulated immunity-related marker genes. To further study the role of in plant defense in vivo, transgenic plants were generated in . Overexpression of in transgenic enhanced innate immunity against DC3000. Furthermore, over-expressing transgenic plants exhibited upregulated transcriptional levels of immunity-associated marker genes, such as , , and . These results collectively confirm the role of as a positive regulator of plant cell death and pepper immunity against bacterial pathogens, which is regulated by signaling synergistically mediated by SA, JA, ET, and ABA.