title: Tissue-specific root ion profiling reveals essential roles of the CAX and ACA calcium transport systems in response to hypoxia in Arabidopsis.
abstract: Waterlogging is a major abiotic stress that limits the growth of plants. The crucial role of Ca(2+) as a second messenger in response to abiotic and biotic stimuli has been widely recognized in plants. However, the physiological and molecular mechanisms of Ca(2+) distribution within specific cell types in different root zones under hypoxia is poorly understood. In this work, whole-plant physiological and tissue-specific Ca(2+) changes were studied using several ACA (Ca(2+)-ATPase) and CAX (Ca(2+)/proton exchanger) knock-out Arabidopsis mutants subjected to waterlogging treatment. In the wild-type (WT) plants, several days of hypoxia decreased the expression of ACA8, CAX4, and CAX11 by 33% and 50% compared with the control. The hypoxic treatment also resulted in an up to 11-fold tissue-dependent increase in Ca(2+) accumulation in root tissues as revealed by confocal microscopy. The increase was much higher in stelar cells in the mature zone of Arabidopsis mutants with loss of function for ACA8, ACA11, CAX4, and CAX11 In addition, a significantly increased Ca(2+) concentration was found in the cytosol of stelar cells in the mature zone after hypoxic treatment. Three weeks of waterlogging resulted in dramatic loss of shoot biomass in cax11 plants (67% loss in shoot dry weight), while in the WT and other transport mutants this decline was only 14-22%. These results were also consistent with a decline in leaf chlorophyll fluorescence (F v/F m). It is suggested that CAX11 plays a key role in maintaining cytosolic Ca(2+) homeostasis and/or signalling in root cells under hypoxic conditions.
authors.affiliation: School of Land and Food, University of Tasmania, Hobart, Tasmania 7001, Australia.
authors.forename: Feifei
authors.initials: F
authors.lastname: Wang
authors.affiliation: School of Science and Health, Western Sydney University, Penrith NSW2751, Australia.
authors.forename: Zhong-Hua
authors.initials: ZH
authors.lastname: Chen
authors.affiliation: School of Science and Health, Western Sydney University, Penrith NSW2751, Australia School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Liu
authors.affiliation: School of Plant Biology and Institute of Agriculture, The University of Western Australia, Crawley, WA 6009, Australia.
authors.forename: Timothy David
authors.initials: TD
authors.lastname: Colmer
authors.affiliation: School of Land and Food, University of Tasmania, Hobart, Tasmania 7001, Australia.
authors.forename: Meixue
authors.initials: M
authors.lastname: Zhou
authors.affiliation: School of Land and Food, University of Tasmania, Hobart, Tasmania 7001, Australia Sergey.Shabala@utas.edu.au.
authors.forename: Sergey
authors.initials: S
authors.lastname: Shabala
mesh_terms: D000693:Anaerobiosis; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D017136:Ion Transport; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D002118:Calcium
keywords: Ca2+-ATPase; Ca2+/proton exchanger; calcium; confocal microscopy; epidermis; hypoxia; potassium; sodium; stele; waterlogging.