title: Rapid regulation of the plasma membrane H⁺-ATPase activity is essential to salinity tolerance in two halophyte species, Atriplex lentiformis and Chenopodium quinoa.
abstract: OBJECTIVE
  The activity of H(+)-ATPase is essential for energizing the plasma membrane. It provides the driving force for potassium retention and uptake through voltage-gated channels and for Na(+) exclusion via Na(+)/H(+) exchangers. Both of these traits are central to plant salinity tolerance; however, whether the increased activity of H(+)-ATPase is a constitutive trait in halophyte species and whether this activity is upregulated at either the transcriptional or post-translation level remain disputed.
  
  
  METHODS
  The kinetics of salt-induced net H(+), Na(+) and K(+) fluxes, membrane potential and AHA1/2/3 expression changes in the roots of two halophyte species, Atriplex lentiformis (saltbush) and Chenopodium quinoa (quinoa), were compared with data obtained from Arabidopsis thaliana roots.
  
  
  RESULTS
  Intrinsic (steady-state) membrane potential values were more negative in A. lentiformis and C. quinoa compared with arabidopsis (-144 ± 3·3, -138 ± 5·4 and -128 ± 3·3 mV, respectively). Treatment with 100 mm NaCl depolarized the root plasma membrane, an effect that was much stronger in arabidopsis. The extent of plasma membrane depolarization positively correlated with NaCl-induced stimulation of vanadate-sensitive H(+) efflux, Na(+) efflux and K(+) retention in roots (quinoa > saltbush > arabidopsis). NaCl-induced stimulation of H(+) efflux was most pronounced in the root elongation zone. In contrast, H(+)-ATPase AHA transcript levels were much higher in arabidopsis compared with quinoa plants, and 100 mm NaCl treatment led to a further 3-fold increase in AHA1 and AHA2 transcripts in arabidopsis but not in quinoa.
  
  
  CONCLUSIONS
  Enhanced salinity tolerance in the halophyte species studied here is not related to the constitutively higher AHA transcript levels in the root epidermis, but to the plant's ability to rapidly upregulate plasma membrane H(+)-ATPase upon salinity treatment. This is necessary for assisting plants to maintain highly negative membrane potential values and to exclude Na(+), or enable better K(+) retention in the cytosol under saline conditions.
authors.affiliation: School of Land and Food, University of Tasmania, Hobart, TAS 7001, Australia, LINV, University of Firenze, Viale delle idee, 30, 50019 Sesto Fiorentino, Italy and College of Life Sciences, Laboratory Centre of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Jayakumar
authors.initials: J
authors.lastname: Bose
authors.affiliation: School of Land and Food, University of Tasmania, Hobart, TAS 7001, Australia, LINV, University of Firenze, Viale delle idee, 30, 50019 Sesto Fiorentino, Italy and College of Life Sciences, Laboratory Centre of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China School of Land and Food, University of Tasmania, Hobart, TAS 7001, Australia, LINV, University of Firenze, Viale delle idee, 30, 50019 Sesto Fiorentino, Italy and College of Life Sciences, Laboratory Centre of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Ana
authors.initials: A
authors.lastname: Rodrigo-Moreno
authors.affiliation: School of Land and Food, University of Tasmania, Hobart, TAS 7001, Australia, LINV, University of Firenze, Viale delle idee, 30, 50019 Sesto Fiorentino, Italy and College of Life Sciences, Laboratory Centre of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Diwen
authors.initials: D
authors.lastname: Lai
authors.affiliation: School of Land and Food, University of Tasmania, Hobart, TAS 7001, Australia, LINV, University of Firenze, Viale delle idee, 30, 50019 Sesto Fiorentino, Italy and College of Life Sciences, Laboratory Centre of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Yanjie
authors.initials: Y
authors.lastname: Xie
authors.affiliation: School of Land and Food, University of Tasmania, Hobart, TAS 7001, Australia, LINV, University of Firenze, Viale delle idee, 30, 50019 Sesto Fiorentino, Italy and College of Life Sciences, Laboratory Centre of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Wenbiao
authors.initials: W
authors.lastname: Shen
authors.affiliation: School of Land and Food, University of Tasmania, Hobart, TAS 7001, Australia, LINV, University of Firenze, Viale delle idee, 30, 50019 Sesto Fiorentino, Italy and College of Life Sciences, Laboratory Centre of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China Sergey.Shabala@utas.edu.au.
authors.forename: Sergey
authors.initials: S
authors.lastname: Shabala
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D017360:Arabidopsis / Q000502:physiology*; D027466:Atriplex / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology; D027465:Chenopodium quinoa / Q000502:physiology*; D017136:Ion Transport; D007700:Kinetics; D008564:Membrane Potentials; D010940:Plant Proteins / Q000378:metabolism*; D018517:Plant Roots / Q000502:physiology; D054712:Salinity; D055049:Salt Tolerance; D055051:Salt-Tolerant Plants / Q000502:physiology; D012965:Sodium Chloride / Q000493:pharmacokinetics*; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D017923:Sodium-Hydrogen Exchangers; D012965:Sodium Chloride; D000251:Adenosine Triphosphatases
keywords: AHA expression; Arabidopsis thaliana; Atriplex lentiformis; Chenopodium quinoa; H+ fluxes; H+-ATPase; K+ fluxes; Na+ fluxes; halophyte; membrane potential; salinity tolerance; saltbush