Abstract
Peptide hormone signaling coordinates plant growth and osmotic stress responses, yet how the transition between these responses is regulated remains poorly understood. Here, we investigated the function of the rice PLANT PEPTIDES CONTAINING SULFATED TYROSINE 8 (OsPSY8) peptide in osmotic stress responses.
OsPSY8
was predominantly expressed in root tissues under nonstress conditions, with preferential expression in lateral roots where it promoted root growth. Osmotic stress rapidly reduced
OsPSY8
expression in roots through the OsWRKY24 transcription factor. Loss-of-function
ospsy8
mutants exhibited enhanced osmotic stress tolerance, whereas
OsPSY8
overexpression increased osmotic stress susceptibility. Transcriptomic analyses revealed that disruption of
OsPSY8
activated stress-responsive pathways, including those associated with lignin biosynthesis, compatible solute production, cell wall remodeling, and reactive oxygen species scavenging, and was accompanied by increased lignin accumulation in roots. In contrast, overexpression of
OsPSY8
resulted in maintenance of growth-associated transcriptional programs while suppressing stress-responsive pathways under osmotic stress. Together, these findings identify OsPSY8 as an important regulator of the transition from growth to stress adaptation in rice and suggest that stress-induced repression of PSY signaling is required to disengage growth programs and activate adaptive responses during osmotic stress.