title: K+ retention in leaf mesophyll, an overlooked component of salinity tolerance mechanism: a case study for barley.
abstract: Plant salinity tolerance is a physiologically complex trait, with numerous mechanisms contributing to it. In this work, we show that the ability of leaf mesophyll to retain K(+) represents an important and essentially overlooked component of a salinity tolerance mechanism. The strong positive correlation between mesophyll K(+) retention ability under saline conditions (quantified by the magnitude of NaCl-induced K(+) efflux from mesophyll) and the overall salinity tolerance (relative fresh weight and/or survival or damage under salinity stress) was found while screening 46 barley (Hordeum vulgare L.) genotypes contrasting in their salinity tolerance. Genotypes with intrinsically higher leaf K(+) content under control conditions were found to possess better K(+) retention ability under salinity and, hence, overall higher tolerance. Contrary to previous reports for barley roots, K(+) retention in mesophyll was not associated with an increased H(+) -pumping in tolerant varieties but instead correlated negatively with this trait. These findings are explained by the fact that increased H(+) extrusion may be needed to charge balance the activity and provide the driving force for the high affinity HAK/KUP K(+) transporters required to restore cytosolic K(+) homeostasis in salt-sensitive genotypes.
authors.affiliation: School of Land and Food, University of Tasmania, Private Bag 54, Hobart, Tas, 7001, Australia.
authors.forename: Honghong
authors.initials: H
authors.lastname: Wu
authors.forename: Min
authors.initials: M
authors.lastname: Zhu
authors.forename: Lana
authors.initials: L
authors.lastname: Shabala
authors.forename: Meixue
authors.initials: M
authors.lastname: Zhou
authors.forename: Sergey
authors.initials: S
authors.lastname: Shabala
mesh_terms: D018533:Biomass; D014644:Genetic Variation; D001467:Hordeum / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D006859:Hydrogen / Q000378:metabolism; D007477:Ions; D058503:Mesophyll Cells / Q000187:drug effects / Q000378:metabolism*; D008954:Models, Biological; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D055049:Salt Tolerance / Q000187:drug effects / Q000235:genetics; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D007477:Ions; D012965:Sodium Chloride; D006859:Hydrogen; D011188:Potassium
keywords: Cytosolic K+ homeostasis; ion flux; membrane potential; membrane transport; tissue tolerance