title: The heterotrimeric G-protein β subunit, AGB1, plays multiple roles in the Arabidopsis salinity response.
abstract: Salinity stress includes both osmotic and ionic toxicity. Sodium homeostasis is influenced by Na(+) uptake and extrusion, vacuolar Na(+) compartmentation and root to shoot Na(+) translocation via transpiration. The knockout mutant of the Arabidopsis heterotrimeric G-protein Gβ subunit, agb1, is hypersensitive to salt, exhibiting a leaf bleaching phenotype. We show that AGB1 is mainly involved in the ionic toxicity component of salinity stress and plays roles in multiple processes of Na(+) homeostasis. agb1 mutants accumulate more Na(+) and less K(+) in both shoots and roots of hydroponically grown plants, as measured by inductively coupled plasma atomic emission spectrometry. agb1 plants have higher root to shoot translocation rates of radiolabelled (24) Na(+) under transpiring conditions, as a result of larger stomatal apertures and increased stomatal conductance. (24) Na(+) tracer experiments also show that (24) Na(+) uptake rates by excised roots of agb1 and wild type are initially equal, but that agb1 has higher net Na(+) uptake at 90 min, implicating possible involvement of AGB1 in the regulation of Na(+) efflux. Calcium alleviates the salt hypersensitivity of agb1 by reducing Na(+) accumulation to below the toxicity threshold. Our results provide new insights into the regulatory pathways underlying plant responses to salinity stress, an important agricultural problem.
authors: Biology Department, Pennsylvania State University, University Park, PA, 16802-5301, USA.
authors: Yunqing
authors: Y
authors: Yu
authors: Biology Department, Pennsylvania State University, University Park, PA, 16802-5301, USA.
authors: Sarah M
authors: SM
authors: Assmann
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D044387:GTP-Binding Protein beta Subunits / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D006706:Homeostasis; D009154:Mutation; D010641:Phenotype; D010937:Plant Growth Regulators / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D054046:Plant Stomata / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D018526:Plant Transpiration; D054712:Salinity; D036226:Seedlings / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D012964:Sodium / Q000378:metabolism*; D012979:Sodium Radioisotopes / Q000032:analysis; D013312:Stress, Physiological
chemical_list: C089590:AGB1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D044387:GTP-Binding Protein beta Subunits; D010937:Plant Growth Regulators; D012979:Sodium Radioisotopes; D002734:Chlorophyll; D000040:Abscisic Acid; D012964:Sodium
keywords: Arabidopsis thaliana; ion homeostasis; salinity; stomatal conductance; transpiration