S-sulfenylation-mediated inhibition of the GSNOR1 activity regulates ovule development in Arabidopsis.

Reactive oxygen species (ROS) and nitric oxide (NO) are two critical classes of signaling molecules that regulate plant development and stress responses. The intracellular level of S-nitrosoglutathione (GSNO), a major bioactive NO species, is regulated by the highly conserved GSNO reductase (GSNOR). However, the molecular mechanisms underlying ROS-mediated regulation of GSNOR remain largely unclear. Here, we show that H₂O₂ negatively regulates the activity of GSNOR1 during ovule development in Arabidopsis. S-sulfenylation of GSNOR1 at Cys-284 inhibits its enzymatic activity. A GSNOR1^C284S mutation causes a reduction of the total SNO level in pistils, thereby disrupting NO homeostasis and eventually leading to defective ovule development. These findings illustrate a unique mechanism by which ROS regulates ovule development through S-sulfenylation-mediated inhibition of the GSNOR activity, thereby establishing a molecular link between ROS and NO signaling pathways in reproductive development.