title: Assessing the role of root plasma membrane and tonoplast Na+/H+ exchangers in salinity tolerance in wheat: in planta quantification methods.
abstract: This work investigates the role of cytosolic Na+ exclusion in roots as a means of salinity tolerance in wheat, and offers in planta methods for the functional assessment of major transporters contributing to this trait. An electrophysiological protocol was developed to quantify the activity of plasma membrane Na+ efflux systems in roots, using the microelectrode ion flux estimation (MIFE) technique. We show that active efflux of Na+ from wheat root epidermal cells is mediated by a SOS1-like homolog, energized by the plasma membrane H+-ATPase. SOS1-like efflux activity was highest in Kharchia 65, a salt-tolerant bread wheat cultivar. Kharchia 65 also had an enhanced ability to sequester large quantities of Na+ into the vacuoles of root cells, as revealed by confocal microscopy using Sodium Green. These findings were consistent with the highest level of expression of both SOS1 and NHX1 transcripts in plant roots in this variety. In the sensitive wheat varieties, a greater proportion of Na+ was located in the root cell cytosol. Overall, our findings suggest a critical role of cytosolic Na+ exclusion for salinity tolerance in wheat and offer convenient protocols to quantify the contribution of the major transporters conferring this trait, to screen plants for salinity tolerance.
authors.affiliation: School of Agricultural Science, University of Tasmania, Private Bag 54, Hobart, Tasmania 7001, AustraliaLINV - DOFI, University of Florence, 50019 Sesto Fiorentino, ItalyAustralian Centre for Plant Functional Genomics, University of Adelaide, Glen Osmond, South Australia, 5064, Australia.
authors.forename: Tracey A
authors.initials: TA
authors.lastname: Cuin
authors.affiliation: School of Agricultural Science, University of Tasmania, Private Bag 54, Hobart, Tasmania 7001, AustraliaLINV - DOFI, University of Florence, 50019 Sesto Fiorentino, ItalyAustralian Centre for Plant Functional Genomics, University of Adelaide, Glen Osmond, South Australia, 5064, Australia.
authors.forename: Jayakumar
authors.initials: J
authors.lastname: Bose
authors.affiliation: School of Agricultural Science, University of Tasmania, Private Bag 54, Hobart, Tasmania 7001, AustraliaLINV - DOFI, University of Florence, 50019 Sesto Fiorentino, ItalyAustralian Centre for Plant Functional Genomics, University of Adelaide, Glen Osmond, South Australia, 5064, Australia.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Stefano
authors.affiliation: School of Agricultural Science, University of Tasmania, Private Bag 54, Hobart, Tasmania 7001, AustraliaLINV - DOFI, University of Florence, 50019 Sesto Fiorentino, ItalyAustralian Centre for Plant Functional Genomics, University of Adelaide, Glen Osmond, South Australia, 5064, Australia.
authors.forename: Deepa
authors.initials: D
authors.lastname: Jha
authors.affiliation: School of Agricultural Science, University of Tasmania, Private Bag 54, Hobart, Tasmania 7001, AustraliaLINV - DOFI, University of Florence, 50019 Sesto Fiorentino, ItalyAustralian Centre for Plant Functional Genomics, University of Adelaide, Glen Osmond, South Australia, 5064, Australia.
authors.forename: Mark
authors.initials: M
authors.lastname: Tester
authors.affiliation: School of Agricultural Science, University of Tasmania, Private Bag 54, Hobart, Tasmania 7001, AustraliaLINV - DOFI, University of Florence, 50019 Sesto Fiorentino, ItalyAustralian Centre for Plant Functional Genomics, University of Adelaide, Glen Osmond, South Australia, 5064, Australia.
authors.forename: Stefano
authors.initials: S
authors.lastname: Mancuso
authors.affiliation: School of Agricultural Science, University of Tasmania, Private Bag 54, Hobart, Tasmania 7001, AustraliaLINV - DOFI, University of Florence, 50019 Sesto Fiorentino, ItalyAustralian Centre for Plant Functional Genomics, University of Adelaide, Glen Osmond, South Australia, 5064, Australia.
authors.forename: Sergey
authors.initials: S
authors.lastname: Shabala
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000378:metabolism; D001671:Biochemistry / Q000379:methods*; D001939:Bread; D002462:Cell Membrane / Q000378:metabolism*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005838:Genotype; D007700:Kinetics; D009154:Mutation / Q000235:genetics; D009997:Osmotic Pressure / Q000187:drug effects; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055049:Salt Tolerance / Q000187:drug effects / Q000235:genetics; D036226:Seedlings / Q000187:drug effects / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D014908:Triticum / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger; D017923:Sodium-Hydrogen Exchangers; D012965:Sodium Chloride; D012964:Sodium; D011188:Potassium