title: Difference in root K+ retention ability and reduced sensitivity of K+-permeable channels to reactive oxygen species confer differential salt tolerance in three Brassica species.
abstract: Brassica species are known to possess significant inter and intraspecies variability in salinity stress tolerance, but the cell-specific mechanisms conferring this difference remain elusive. In this work, the role and relative contribution of several key plasma membrane transporters to salinity stress tolerance were evaluated in three Brassica species (B. napus, B. juncea, and B. oleracea) using a range of electrophysiological assays. Initial root growth assay and viability staining revealed that B. napus was most tolerant amongst the three species, followed by B. juncea and B. oleracea At the mechanistic level, this difference was conferred by at least three complementary physiological mechanisms: (i) higher Na(+) extrusion ability from roots resulting from increased expression and activity of plasma membrane SOS1-like Na(+)/H(+) exchangers; (ii) better root K(+) retention ability resulting from stress-inducible activation of H(+)-ATPase and ability to maintain more negative membrane potential under saline conditions; and (iii) reduced sensitivity of B. napus root K(+)-permeable channels to reactive oxygen species (ROS). The last two mechanisms played the dominant role and conferred most of the differential salt sensitivity between species. Brassica napus plants were also more efficient in preventing the stress-induced increase in GORK transcript levels and up-regulation of expression of AKT1, HAK5, and HKT1 transporter genes. Taken together, our data provide the mechanistic explanation for differential salt stress sensitivity amongst these species and shed light on transcriptional and post-translational regulation of key ion transport systems involved in the maintenance of the root plasma membrane potential and cytosolic K/Na ratio as a key attribute for salt tolerance in Brassica species.
authors.affiliation: Department of Plant Physiology, ICAR-Directorate of Groundnut Research, Junagadh, Gujarat-362 001, India School of Land and Food and Tasmanian Institute for Agriculture, University of Tasmania, Hobart, Private Bag 94, Tas 7001, Australia.
authors.forename: Koushik
authors.initials: K
authors.lastname: Chakraborty
authors.affiliation: School of Land and Food and Tasmanian Institute for Agriculture, University of Tasmania, Hobart, Private Bag 94, Tas 7001, Australia.
authors.forename: Jayakumar
authors.initials: J
authors.lastname: Bose
authors.affiliation: School of Land and Food and Tasmanian Institute for Agriculture, University of Tasmania, Hobart, Private Bag 94, Tas 7001, Australia.
authors.forename: Lana
authors.initials: L
authors.lastname: Shabala
authors.affiliation: School of Land and Food and Tasmanian Institute for Agriculture, University of Tasmania, Hobart, Private Bag 94, Tas 7001, Australia Sergey.Shabala@utas.edu.au.
authors.forename: Sergey
authors.initials: S
authors.lastname: Shabala
mesh_terms: D001937:Brassica / Q000378:metabolism / Q000502:physiology*; D029688:Brassica napus / Q000378:metabolism / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D009149:Mustard Plant / Q000378:metabolism / Q000502:physiology*; D018517:Plant Roots / Q000378:metabolism / Q000502:physiology*; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D055049:Salt Tolerance / Q000502:physiology*
chemical_list: D015221:Potassium Channels; D017382:Reactive Oxygen Species; D000252:Calcium-Transporting ATPases; D011188:Potassium
keywords: H+-ATPase; ROS detoxification; ion homeostasis; membrane potential; potassium retention; sodium exclusion; tissue tolerance.