title: Phytosulfokine-α controls hypocotyl length and cell expansion in Arabidopsis thaliana through phytosulfokine receptor 1.
abstract: The disulfated peptide growth factor phytosulfokine-α (PSK-α) is perceived by LRR receptor kinases. In this study, a role for PSK signaling through PSK receptor PSKR1 in Arabidopsis thaliana hypocotyl cell elongation is established. Hypocotyls of etiolated pskr1-2 and pskr1-3 seedlings, but not of pskr2-1 seedlings were shorter than wt due to reduced cell elongation. Treatment with PSK-α did not promote hypocotyl growth indicating that PSK levels were saturating. Tyrosylprotein sulfotransferase (TPST) is responsible for sulfation and hence activation of the PSK precursor. The tpst-1 mutant displayed shorter hypocotyls with shorter cells than wt. Treatment of tpst-1 seedlings with PSK-α partially restored elongation growth in a dose-dependent manner. Hypocotyl elongation was significantly enhanced in tpst-1 seedlings at nanomolar PSK-α concentrations. Cell expansion was studied in hypocotyl protoplasts. WT and pskr2-1 protoplasts expanded in the presence of PSK-α in a dose-dependent manner. By contrast, pskr1-2 and pskr1-3 protoplasts were unresponsive to PSK-α. Protoplast swelling in response to PSK-α was unaffected by ortho-vanadate, which inhibits the plasma membrane H(+)-ATPase. In maize (Zea mays L.), coleoptile protoplast expansion was similarly induced by PSK-α in a dose-dependent manner and was dependent on the presence of K(+) in the media. In conclusion, PSK-α signaling of hypocotyl elongation and protoplast expansion occurs through PSKR1 and likely involves K(+) uptake, but does not require extracellular acidification by the plasma membrane H(+)-ATPase.
authors.affiliation: Entwicklungsbiologie und Physiologie der Pflanzen, Universität Kiel, Kiel, Germany.
authors.forename: Nils
authors.initials: N
authors.lastname: Stührwohldt
authors.forename: Renate I
authors.initials: RI
authors.lastname: Dahlke
authors.forename: Bianka
authors.initials: B
authors.lastname: Steffens
authors.forename: Amanda
authors.initials: A
authors.lastname: Johnson
authors.forename: Margret
authors.initials: M
authors.lastname: Sauter
mesh_terms: D017360:Arabidopsis / Q000166:cytology*; D029681:Arabidopsis Proteins / Q000502:physiology*; D001483:Base Sequence; D017931:DNA Primers; D006863:Hydrogen-Ion Concentration; D018546:Hypocotyl / Q000166:cytology*; D036361:Peptide Hormones; D010940:Plant Proteins / Q000378:metabolism / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers; C100975:PSK-alpha protein, plant; C515018:PSKR1 protein, Arabidopsis; D036361:Peptide Hormones; D010940:Plant Proteins; D011956:Receptors, Cell Surface