Abstract
Cis-natural antisense transcript ELENA19 attenuates PAMP-triggered immunity by modulating ABA- and PAMP-inducible UGT71B6 expression, resulting in increased ABA levels and reduced ET-dependent flg22-induced callose deposition in Arabidopsis. Long noncoding RNAs (lncRNAs) have emerged as crucial regulators of various biological processes. However, the roles of lncRNAs in pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) remain largely unexplored in plants. Based on our previous custom lncRNA array analysis of Arabidopsis seedlings treated with PAMPs (elf18 and flg22), we identified a novel ELF18-INDUCED LONG NONCODING RNA, ELENA19. In this study, we characterized the function of ELENA19 as a natural antisense transcript of UDP-glycosyltransferase 71B6 (UGT71B6), which is responsible for the glycosylation of abscisic acid (ABA). ELENA19 expression was rapidly upregulated upon treatment with ABA or PAMPs (flg22 and elf18). Among the genes neighboring ELENA19, only UGT71B6 was responsive to both ABA and PAMP treatments. UGT71B6 expression was significantly attenuated in ELENA19-overexpressing (OX) plants compared to wild-type (WT) plants after PAMP or ABA treatment. ELENA19 OX plants were hypersensitive to ABA during germination and had higher endogenous ABA levels than WT plants, suggesting that ELENA19 down-regulates UGT71B6 expression and enhances endogenous ABA levels. Flg22-triggered callose deposition was reduced, and the expression of ethylene (ET)-dependent Flg22-induced genes was significantly down-regulated in ELENA19 OX plants compared to WT plants, confirming the antagonistic interaction between ABA and ET signaling in the flg22-mediated immune response. These results demonstrate that ELENA19 attenuates PAMP-triggered immunity by modulating UGT71B6 expression.