Signaling by a tyrosine-sulfated peptide balances growth and osmotic stress response in rice

The transition between plant growth and osmotic stress responses in rice involves a signaling molecule known as the PLANT PEPTIDES CONTAINING SULFATED TYROSINE 8 (OsPSY8) peptide. This peptide is predominantly expressed in root tissues under non-stress conditions, with a preference for lateral roots, where it promotes root growth.

When rice plants encounter osmotic stress, OsPSY8 expression rapidly declines in roots, mediated by the OsWRKY24 transcription factor. The absence of OsPSY8 leads to enhanced tolerance to osmotic stress, while its overexpression results in increased susceptibility to such stress.

Genetic investigations uncovered that the disruption of OsPSY8 activation of stress-responsive pathways, including those related to lignin biosynthesis, production of compatible solutes, remodeling of cell walls, and scavenging of reactive oxygen species (ROS). These changes are accompanied by an increase in lignin accumulation in roots. Conversely, overexpression of OsPSY8 maintains growth-associated transcriptional programs while suppressing stress-responsive pathways when rice plants face osmotic stress.

These findings highlight the crucial role of OsPSY8 in the transition from growth to stress adaptation in rice. They suggest that stress-induced repression of the PSY signaling pathway is necessary to dismantle growth programs and activate adaptive responses during osmotic stress.