title: Plasma Membrane Ca2+-Permeable Channels are Differentially Regulated by Ethylene and Hydrogen Peroxide to Generate Persistent Plumes of Elevated Cytosolic Ca2+ During Transfer Cell Trans-Differentiation.
abstract: The enhanced transport capability of transfer cells (TCs) arises from their ingrowth wall architecture comprised of a uniform wall on which wall ingrowths are deposited. The wall ingrowth papillae provide scaffolds to amplify plasma membranes that are enriched in nutrient transporters. Using Vicia faba cotyledons, whose adaxial epidermal cells spontaneously and rapidly (hours) undergo a synchronous TC trans-differentiation upon transfer to culture, has led to the discovery of a cascade of inductive signals orchestrating deposition of ingrowth wall papillae. Auxin-induced ethylene biosynthesis initiates the cascade. This in turn drives a burst in extracellular H2O2 production that triggers uniform wall deposition. Thereafter, a persistent and elevated cytosolic Ca(2+) concentration, resulting from Ca(2+) influx through plasma membrane Ca(2+)-permeable channels, generates a Ca(2+) signal that directs formation of wall ingrowth papillae to specific loci. We now report how these Ca(2+)-permeable channels are regulated using the proportionate responses in cytosolic Ca(2+) concentration as a proxy measure of their transport activity. Culturing cotyledons on various combinations of pharmacological agents allowed the regulatory influence of each upstream signal on Ca(2+) channel activity to be evaluated. The findings demonstrated that Ca(2+)-permeable channel activity was insensitive to auxin, but up-regulated by ethylene through two independent routes. In one route ethylene acts directly on Ca(2+)-permeable channel activity at the transcriptional and post-translational levels, through an ethylene receptor-dependent pathway. The other route is mediated by an ethylene-induced production of extracellular H2O2 which then acts translationally and post-translationally to up-regulate Ca(2+)-permeable channel activity. A model describing the differential regulation of Ca(2+)-permeable channel activity is presented.
authors.affiliation: School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW, 2308 Australia.
authors.forename: Hui-ming
authors.initials: HM
authors.lastname: Zhang
authors.affiliation: School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, NSW, 2308 Australia.
authors.forename: Dirk F
authors.initials: DF
authors.lastname: van Helden
authors.affiliation: School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW, 2308 Australia.
authors.forename: David W
authors.initials: DW
authors.lastname: McCurdy
authors.affiliation: School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW, 2308 Australia.
authors.forename: Christina E
authors.initials: CE
authors.lastname: Offler
authors.affiliation: School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW, 2308 Australia John.Patrick@newcastle.edu.au.
authors.forename: John W
authors.initials: JW
authors.lastname: Patrick
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects*; D054338:Cell Transdifferentiation / Q000187:drug effects*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism*; D005030:Ethylenes / Q000494:pharmacology*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007210:Indoleacetic Acids / Q000494:pharmacology; D008954:Models, Biological; D059828:Plant Cells / Q000187:drug effects / Q000378:metabolism; D019441:Plant Epidermis / Q000166:cytology / Q000187:drug effects; D014176:Protein Biosynthesis / Q000187:drug effects; D011956:Receptors, Cell Surface / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects; D031307:Vicia faba / Q000166:cytology / Q000187:drug effects
chemical_list: D005030:Ethylenes; D007210:Indoleacetic Acids; D011956:Receptors, Cell Surface; C036216:ethylene; D006861:Hydrogen Peroxide; D002118:Calcium
keywords: Ca2+-permeable channels; Cytosolic Ca2+ concentration; Ethylene; ROS; Transfer cell; Vicia faba