Abstract
Abstract
High temperature increasingly threatens crop growth and yield under climate change. Plants rely on phytohormone signalling to adapt to heat stress, yet the underlying mechanisms remain poorly understood. One of the plant hormone receptors, the jasmonate receptor CORONATINE-INSENSITIVE 1 (COI1), plays an essential role in conferring plant thermotolerance. However, to date, the molecular mechanisms by which COI1 mediates plant high temperature tolerance remain enigmatic. Here, we characterise moderately high temperature-regulated differential phosphorylation of TaCOI1-1D, one of the wheat COI1 homeologous proteins. We show that TaCOI1-1D is a functional component of the Skp1–Cullin–F-box COI1 (SCF
COI1
) complex and that its heat-regulated phosphosite, Ser16, is conserved with Thr16 in Arabidopsis COI1. Mutating this site enhances the COI1– ARABIDOPSIS SKP1 HOMOLOGUE 1 (ASK1) interaction in both wheat and Arabidopsis. We further demonstrate that Arabidopsis COI1 interacts with the nucleocytosolic monothiol glutaredoxin glutaredoxin S17 (GRXS17). The enhanced COI1–ASK1 binding stabilizes COI1 and promotes the release of GRXS17, allowing the formation of GRXS17 oligomers, a possibly essential state for AtGRXS17’s function in regulating H
2
O
2
scavenging and enhancing thermotolerance in Arabidopsis. Our findings reveal a mechanism in which a moderately high temperature-induced modification of the JA receptor simultaneously stabilizes the receptor and orchestrates redox-dependent thermotolerance.