Abstract: The plant hormone jasmonate (JA) regulates plant growth and immunity by orchestrating a genome-wide transcriptional reprogramming. In the resting stage, JASMONATE-ZIM DOMAIN (JAZ) proteins act as main repressors to regulate the expression of JA-responsive genes in the JA signaling pathway. However, the mechanisms underlying de-repression of JA-responsive genes in response to JA treatment remain elusive. Here, we report two nuclear factor Y transcription factors NF-YB2 and NF-YB3 (thereafter YB2 and YB3) play key roles in such de-repression in Arabidopsis. YB2 and YB3 function redundantly and positively regulate plant resistance against the necrotrophic pathogen Botrytis cinerea, which are specially required for transcriptional activation of a set of JA-responsive genes following inoculation. Furthermore, YB2 and YB3 modulated their expression through direct occupancy and interaction with histone demethylase Ref6 to remove repressive histone modifications. Moreover, YB2 and YB3 physically interacted with JAZ repressors and negatively modulated their abundance, which in turn attenuated the inhibition of JAZ proteins on the transcription of JA-responsive genes, thereby activating JA response and promoting disease resistance. Overall, our study reveals the positive regulators of YB2 and YB3 in JA signaling by positively regulating transcription of JA-responsive genes and negatively modulating the abundance of JAZ proteins.

Key words: histone demethylase, jasmonate response, JAZ repressor, necrotrophic resistance, nuclear factor