title: The Camelina aquaporin CsPIP2;1 is regulated by phosphorylation at Ser273, but not at Ser277, of the C-terminus and is involved in salt- and drought-stress responses.
abstract: Aquaporin (AQP) proteins are involved in water homeostasis in cells at all taxonomic levels of life. Phosphorylation of some AQPs has been proposed to regulate water permeability via gating of the channel itself. We analyzed plasma membrane intrinsic proteins (PIP) from Camelina and characterized their biological functions under both stressful and favorable conditions. A three-dimensional theoretical model of the Camelina AQP proteins was built by homology modeling which could prove useful in further functional characterization of AQPs. CsPIP2;1 was strongly and constitutively expressed in roots and leaves of Camelina, suggesting that this gene is related to maintenance of homeostasis during salt and drought stresses. CsPIP2s exhibited water channel activity in Xenopus oocytes. We then examined the roles of CsPIP2;1 phosphorylation at Ser273 and Ser277 in the regulation of water permeability using phosphorylation mutants. A single deletion strain of CsPIP2;1 was generated to serve as the primary host for testing AQP expression constructs. A Ser277 to alanine mutation (to prevent phosphorylation) did not change CsPIP2;1 water permeability while a Ser273 mutation to alanine did affect water permeability. Furthermore, a CsPIP2;1 point mutation when ectopically expressed in yeast resulted in lower growth in salt and drought conditions compared with controls, and confirmation of Ser273 as the phosphorylation site. Our results support the idea that post-translational modifications in the Ser273 regulatory domains of the C-terminus fine tune water flux through CsPIP2;1.
authors.affiliation: Department of Bioenergy Science and Technology, Chonnam National University, Gwangju 500-757, Republic of Korea.
authors.forename: Ha-Young
authors.initials: HY
authors.lastname: Jang
authors.affiliation: Department of Experimental Plant Biology, Faculty of Science, University of South Bohemia, Branisovska 31, Ceske Budejovice, Czech Republic.
authors.forename: Jiye
authors.initials: J
authors.lastname: Rhee
authors.affiliation: Department of Bioenergy Science and Technology, Chonnam National University, Gwangju 500-757, Republic of Korea; Department of Ecosystem Science and Management, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: John E
authors.initials: JE
authors.lastname: Carlson
authors.affiliation: Department of Bioenergy Science and Technology, Chonnam National University, Gwangju 500-757, Republic of Korea. Electronic address: asjsuse@chonnam.ac.kr.
authors.forename: Sung-Ju
authors.initials: SJ
authors.lastname: Ahn
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D019607:Brassicaceae / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D055864:Droughts; D005260:Female; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009154:Mutation; D009865:Oocytes; D010766:Phosphorylation; D010802:Phylogeny; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D012694:Serine; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological; D014867:Water / Q000378:metabolism; D014981:Xenopus
chemical_list: D020346:Aquaporins; D010940:Plant Proteins; D014867:Water; D012965:Sodium Chloride; D012694:Serine
keywords: CsPIP2 ;1; Drought; Phosphorylation; Salt; Ser273