Abstract
Phytosulfokine (PSK), a 5-amino-acid secreted peptide, promotes cellular proliferation, tracheary element differentiation, and somatic embryo formation in vitro. Genes encoding PSK precursors are expressed at considerable level in a variety of tissues throughout plant life cycle, suggesting a role in plant development as well as in vitro culture. The PSK receptor PSKR1 was purified from microsomal fractions of carrot cells by ligand-based affinity chromatography and identified as a member of leucine-rich repeat receptor kinase (LRR-RK). Disruption and overexpression of Arabidopsis ortholog of PSKR1 (AtPSKR1) affects cellular longevity and potential for growth during plant development as well as in vitro culture. We further identified two proteins from the Arabidopsis genome, tentatively designated AtPSKR2 and AtPSKR3, with high sequence identity to AtPSKR1. Here we report the results of a series of experiments including complementation tests, expression patterns, PSK-binding activities of AtPSKR2 and AtPSKR3, and phenotypes of multiple knockout mutants of AtPSKR genes.
