Physiological and molecular mechanisms mediating xylem Na+ loading in barley in the context of salinity stress tolerance

• Published in: Plant, cell and environment Vol. 40; no. 7; pp. 1009 - 1020
• Main Authors: Zhu, Min, Zhou, Meixue, Shabala, Lana, Shabala, Sergey
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.07.2017
• Subjects: ABA; Abscisic acid; Abscisic Acid - metabolism; Abscisic Acid - pharmacology; Barley; Bumetanide; Calcium; Calcium influx; CCC transporter; Chlorides; Fluxes; Gene Expression Regulation, Plant; Genotypes; H2O2; Hordeum - drug effects; Hordeum - genetics; Hordeum - physiology; Hydrogen peroxide; Hydrogen Peroxide - pharmacology; Kinetics; Molecular modelling; NAD(P)H oxidase; NADPH oxidase; Oxidase; Parenchyma; Plant Proteins - genetics; Plant Proteins - metabolism; Potassium - metabolism; Reactive oxygen species; Salinity; Salinity effects; Salinity tolerance; Salts; Signaling; SKOR; Sodium - metabolism; SOS1; Stress; Stress, Physiological - physiology; Stresses; Thiourea - pharmacology; Transcription; Xylem; Xylem - drug effects; Xylem - metabolism; xylem sodium loading; ABA; CCC transporter; NADPH oxidase; xylem sodium loading; H2O2; SOS1; SKOR
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.12727

Time‐dependent kinetics of xylem Na+ loading was investigated using a large number of barley genotypes contrasting in their salinity tolerance. Salt‐sensitive varieties were less efficient in controlling xylem Na+ loading and showed a gradual increase in the xylem Na+ content over the time. To understand underlying ionic and molecular mechanisms, net fluxes of Ca2+, K+ and Na+ were measured from the xylem parenchyma tissue in response to H2O2 and ABA; both of them associated with salinity stress signalling. Our results indicate that NADPH oxidase‐mediated apoplastic H2O2 production acts upstream of the xylem Na+ loading and is causally related to ROS‐inducible Ca2+ uptake systems in the root stelar tissue. It was also found that ABA regulates (directly or indirectly) the process of Na+ retrieval from the xylem and the significant reduction of Na+ and K+ fluxes induced by bumetanide are indicative of a major role of chloride cation co‐transporter (CCC) on xylem ion loading. Transcript levels of HvHKT1;5_like and HvSOS1_like genes in the root stele were observed to decrease after salt stress, while there was an increase in HvSKOR_like gene, indicating that these ion transporters are involved in primary Na+/K+ movement into/out of xylem.