title: Phytosulfokine peptide signalling.
abstract: Phytosulfokine (PSK) belongs to the group of plant peptide growth factors. It is a disulfated pentapeptide encoded by precursor genes that are ubiquitously present in higher plants, suggestive of universal functions. Processing of the preproprotein involves sulfonylation by a tyrosylprotein sulfotransferase in the trans-golgi and proteolytic cleavage in the apoplast. The secreted peptide is perceived at the cell surface by a membrane-bound receptor kinase of the leucine-rich repeat family. The PSK receptor PSKR1 from Arabidopsis thaliana is an active kinase and has guanylate cyclase activity resulting in dual-signal outputs. Receptor activity is regulated by calmodulin. While PSK may be an autocrine growth factor, it also acts non-cell autonomously by promoting growth of cells that are receptor-deficient. In planta, PSK has multiple functions. It promotes cell growth, acts in the quiescent centre cells of the root apical meristem, contributes to funicular pollen tube guidance, and differentially alters immune responses depending on the pathogen. It has been suggested that PSK integrates growth and defence signals to balance the competing metabolic costs of these responses. This review summarizes our current understanding of PSK synthesis, signalling, and activity.
authors.affiliation: Plant Developmental Biology and Plant Physiology, University of Kiel, Am Botanischen Garten 5, 24118 Kiel, Germany msauter@bot.uni-kiel.de.
authors.forename: Margret
authors.initials: M
authors.lastname: Sauter
mesh_terms: D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D010937:Plant Growth Regulators / Q000235:genetics* / Q000378:metabolism; D018521:Plant Physiological Phenomena; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D011498:Protein Precursors / Q000235:genetics* / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; C515018:PSKR1 protein, Arabidopsis; D010937:Plant Growth Regulators; D010940:Plant Proteins; D011498:Protein Precursors; D011956:Receptors, Cell Surface
keywords: Calmodulin; cGMP; cell elongation; defence; guanylate cyclase; leucine-rich repeat receptor kinase; phosphorylation; phytosulfokine; reproduction; sulfated peptide growth factor.