Abstract
Phytosulfokine (PSK), a 5-amino-acid sulfated peptide that has been detected in conditioned medium of plant cell culture, 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 including leaves, stems and roots as well as callus, throughout plant life cycle, suggesting a role in plant development as well as in vitro culture. The PSK receptor 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). This LRR-RLK has been named PSKR1. The carrot PSKR1 exhibits a high percentage of amino acid identity with an LRR-RLK found in Arabidopsis. The in planta function of PSK is currently being researched using its Arabidopsis loss-of-function mutant. We will summarize the current knowledge and recent advances in the functional analysis of PSK and PSKR1.
