title: A vacuolar antiporter is differentially regulated in leaves and roots of the halophytic wild rice Porteresia coarctata (Roxb.) Tateoka.
abstract: Vacuolar NHX-type antiporters play a role in Na(+)/K(+) uptake that contributes to growth, nutrition and development. Under salt/osmotic stress they mediate the vacuolar compartmentalization of K(+)/Na(+), thereby preventing toxic Na(+)K(+) ratios in the cytosol. Porteresia coarctata (Roxb.) Tateoka, a mangrove associate, is a distant wild relative of cultivated rice and is saline as well as submergence tolerant. A vacuolar NHX homolog isolated from a P. coarctata cDNA library (PcNHX1) shows 96 % identity (nucleotide level) to OsNHX1. Diurnal PcNHX1 expression in leaves was found to be largely unaltered, though damped by salinity. PcNHX1 promoter directed GUS expression is phloem-specific in leaves, stem and roots of transgenic plants in the absence of stress. Under NaCl stress, GUS expression was also seen in the epidermal and sub-epidermal layers (mesophyll, guard cells and trichomes) of leaves, root tip. The salinity in the rhizosphere of P. coarctata varies considerably due to diurnal/semi-diurnal tidal inundation. The diurnal expression of PcNHX1 in leaves and salinity induced expression in roots may have evolved in response to dynamic changes in salinity of in the P. coarctata rhizosphere. Despite high sequence conservation between OsNHX1 and PcNHX1, the distinctive expression pattern of PcNHX1 exemplifies how variation in expression is fine tuned to suit the halophytic growth habitat of a plant.
authors.affiliation: Department of Plant Molecular Biology, M.S. Swaminathan Research Foundation, III Cross Street, Taramani Institutional Area, Chennai, 600113, India.
authors.forename: Praseetha
authors.initials: P
authors.lastname: Kizhakkedath
authors.forename: Vidya
authors.initials: V
authors.lastname: Jegadeeson
authors.forename: Gayatri
authors.initials: G
authors.lastname: Venkataraman
authors.forename: Ajay
authors.initials: A
authors.lastname: Parida
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D000595:Amino Acid Sequence; D015152:Blotting, Northern; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000494:pharmacology; D018515:Plant Leaves / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055051:Salt-Tolerant Plants / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism
chemical_list: D010937:Plant Growth Regulators; D010940:Plant Proteins; D017923:Sodium-Hydrogen Exchangers; D012965:Sodium Chloride; D000040:Abscisic Acid; D005966:Glucuronidase