The NAC transcription factor RIM1 of rice is a new regulator of jasmonate signaling

Abstract

Jasmonates (JAs) are lipid-derived regulators that play crucial roles in both host immunity and development. We recently identified the NAC transcription factor RIM1 as a host factor involved in multiplication of rice dwarf virus (RDV). Here, we report that RIM1 functions as a transcriptional regulator of JA signaling and is degraded in response to JA treatment via a 26S proteasome-dependent pathway. Plants carrying rim1 mutations show a phenotype of root growth inhibition. The expression profiles of the mutants were significantly correlated with those of JA-treated wild-type plants without accumulation of endogenous JA, indicating that RIM1 functions as a component of JA signaling. The expression of genes encoding JA biosynthetic enzymes (lipoxygenase (LOX), allene oxide synthase 2 (AOS2) and OPDA reductase 7 (OPR7)) was up-regulated in the rim1 mutants under normal conditions, and a rapid and massive accumulation of endogenous JA was detected in the mutants after wounding. These results suggest that RIM1 may represent a new molecular link in jasmonate signaling, and may thereby provide new insights into the well-established coronatine-insensitive 1 (COI1)-Jasmonate ZIM-domain (JAZ) JA signaling pathway.