A signaling cascade mediating fruit trait development via phosphorylation‐modulated nuclear accumulation of JAZ repressor

ABSTRACT It is generally accepted that jasmonate‐ZIM domain (JAZ) repressors act to mediate jasmonate (JA) signaling via CORONATINE‐INSENSITIVE1 (COI1)‐mediated degradation. Here, we report a cryptic signaling cascade where a JAZ repressor, FvJAZ12, mediates multiple signaling inputs via phosphorylation‐modulated subcellular translocation rather than the COI1‐mediated degradation mechanism in strawberry (Fragaria vesca). FvJAZ12 acts to regulate flavor metabolism and defense response, and was found to be the target of FvMPK6, a mitogen‐activated protein kinase that is capable of responding to multiple signal stimuli. FvMPK6 phosphorylates FvJAZ12 at the amino acid residues S179 and T183 adjacent to the PY residues, thereby attenuating its nuclear accumulation and relieving its repression for FvMYC2, which acts to control the expression of lipoxygenase 3 (FvLOX3), an important gene involved in JA biosynthesis and a diverse array of cellular metabolisms. Our data reveal a previously unreported mechanism for JA signaling and decipher a signaling cascade that links multiple signaling inputs with fruit trait development. The strawberry MAP kinase FvMPK6 kinase phosphorylates the jasmonate‐ZIM domain repressor FvJAZ12, derepressing its inhibition of FvMYC2, which controls expression of the lipoxygenase gene FvLOX3, which is implicated in regulating strawberry fruit quality.