A rice TIFY/ZIM-motif protein is a negative regulator in the jasmonate signaling and controls plant growth by activating cell division

Abstract

We have been employing the Full-length cDNA Over-eXpresser gene (FOX) hunting system with transgenic rice plants for the genome-wide elucidation of rice gene functions. Among many FOX-rice plants, two lines showed promotion of internode elongation, early flowering and increase in endosperm size. Microscopic observation revealed that the growth promotion was caused by enhancement of cell division in the tissues, not by cell elongation. Both the lines had an identical transgene encoding a protein with TIFY/ZIM motif, which was designated FR29. Arabidopsis JAZ (JASMONATE ZIM-DOMAIN) proteins are reported to be transcriptional repressor(s) of the JA-responsive genes and the targets of SCF^COI1 ubiquitin ligase in the jasmonate (JA) signaling (Thines et al. 2007). The FR29-FOX rice plants exhibited reduced responses to JA and inhibition of JA-inducible gene expression. Our results suggest that the TIFY-motif-containing protein of rice regulates plant growth through negative regulation of the JA signaling.