title: Salt stress sensing and early signalling events in plant roots: Current knowledge and hypothesis.
abstract: Soil salinity is a major environmental constraint to crop production. While the molecular identity and functional expression of Na(+) transport systems mediating Na(+) exclusion from the cytosol has been studied in detail, far less is known about the mechanisms by which plants sense high Na(+) levels in the soil and the rapid signalling events that optimise plant performance under saline conditions. This review aims to fill this gap. We first discuss the nature of putative salt stress sensors, candidates which include Na(+) transport systems, mechanosensory proteins, proteins with regulatory Na(+) binding sites, sensing mediated by cyclic nucleotide-gated channels, purine receptors, annexin and voltage gating. We suggest that several transport proteins may be clustered together to form a microdomain in a lipid raft, allowing rapid changes in the activity of an individual protein to be translated into stress-induced Ca(2+) and H2O2 signatures. The pathways of stress signalling to downstream targets are discussed, and the kinetics and specificity of salt stress signalling between glycophytes and halophytes is compared. We argue that these sensing mechanisms operate in parallel, providing plants with a robust system for decoding information about the specific nature and severity of the imposed salt stress.
authors.affiliation: School of Land and Food, University of Tasmania, Private Bag 54, Hobart, Tasmania 7001, Australia. Electronic address: Sergey.Shabala@utas.edu.au.
authors.forename: Sergey
authors.initials: S
authors.lastname: Shabala
authors.affiliation: School of Land and Food, University of Tasmania, Private Bag 54, Hobart, Tasmania 7001, Australia.
authors.forename: Honghong
authors.initials: H
authors.lastname: Wu
authors.affiliation: School of Land and Food, University of Tasmania, Private Bag 54, Hobart, Tasmania 7001, Australia; ARC Centre of Excellence in Plant Energy Biology and School of Agriculture, Food and Wine, University of Adelaide, PMB 1, Glen Osmond, SA 5064, Australia.
authors.forename: Jayakumar
authors.initials: J
authors.lastname: Bose
mesh_terms: D018506:Gene Expression Regulation, Plant; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D055049:Salt Tolerance; D055051:Salt-Tolerant Plants / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects; D012965:Sodium Chloride / Q000494:pharmacology*
chemical_list: D012965:Sodium Chloride
keywords: Annexin; Ca(2+) signature; Cyclic nucleotides; H(+)-ATPase; Lipid raft; Mechanosensory proteins; Membrane potential; Na(+) binding sites; Potassium; Purine; ROS; Voltage gating