From biosynthesis to signaling: unveiling the multifaceted roles of phytosulfokine peptide in plants

Phytosulfokine (PSK) is a secreted peptide that plays a pivotal role in regulating plant growth, development, and environmental adaptability. PSK biosynthesis begins with a pre-proprotein precursor that undergoes sulfation by tyrosylprotein sulfotransferase in the cis-Golgi apparatus, followed by proteolytic cleavage by subtilases in the apoplast to yield the mature PSK. This mature peptide is recognized by membrane-bound leucine-rich repeat receptor kinases, known as PSK receptors (PSKRs), which subsequently activate diverse signaling cascades, including cGMP-dependent signaling, phosphorylation events, Ca2+ signaling, mitogen-activated protein kinase pathways, and transcriptional regulation. This review consolidates recent advances in PSK biosynthesis, biological functions, signaling mechanisms, and crosstalk with other plant hormones. By summarizing these insights, we aim to provide a theoretical framework for developing PSK-based strategies to enhance crop resilience and productivity in response to environmental challenges.