The redox-phytohormone nexus, illustrated by the jasmonate paradigm.

Redox-sensitive protein switches and transcriptional networks are integral to phytohormone signaling networks. The jasmonate (JA) signaling pathway, which incorporates the coronatine insensitive 1 (COI1)-Jasmonate ZIM-domain (JAZ) co-receptor and the MYC2 transcription factor, is a relatively recent evolutionary innovation that has emerged only in land plants. Earlier JA signaling systems relied on electrophilic oxylipins, such as 12-oxo-phytodienoic acid (OPDA) and dinor-12-oxo-10,15(Z)-phytodienoic acid (dn-OPDA), and reactive oxygen species (ROS), particularly H2O2. All plant 14-3-3 proteins, such as General regulatory factor 8 (GRF8), contain a conserved redox-sensitive cysteine. Sulfenylation of GRF8 relieves inhibition of MYC2, thereby facilitating JA signaling in arabidopsis (Arabidopsis thaliana). This mechanism may represent a primordial oxylipin signaling system, overlain by the more recent COI1-JAZ system, revealing hormone signaling plasticity that can be targeted for engineering stress-resilient crops.