An Arabidopsis soil-salinity-tolerance mutation confers ethylene-mediated enhancement of sodium/potassium homeostasis

Abstract

High soil Na concentrations damage plants by increasing cellular Na accumulation and K loss. Excess soil Na stimulates ethylene-induced soil-salinity tolerance, the mechanism of which we here define via characterization of an Arabidopsis thaliana mutant displaying transpiration-dependent soil-salinity tolerance. This phenotype is conferred by a loss-of-function allele of ETHYLENE OVERPRODUCER1 (ETO1; mutant alleles of which cause increased production of ethylene). We show that lack of ETO1 function confers soil-salinity tolerance through improved shoot Na/K homeostasis, effected via the ETHYLENE RESISTANT1-CONSTITUTIVE TRIPLE RESPONSE1 ethylene signaling pathway. Under transpiring conditions, lack of ETO1 function reduces root Na influx and both stelar and xylem sap Na concentrations, thereby restricting root-toshoot delivery of Na. These effects are associated with increased accumulation of RESPIRATORY BURST OXIDASE HOMOLOG F (RBOHF)-dependent reactive oxygen species in the root stele. Additionally, lack of ETO1 function leads to significant enhancement of tissue K status by an RBOHF-independent mechanism associated with elevated HIGH-AFFINITY K+ TRANSPORTER5 transcript levels. We conclude that ethylene promotes soil-salinity tolerance via improved Na/K homeostasis mediated by RBOHF-dependent regulation of Na accumulation and RBOHF-independent regulation of K accumulation. © 2013 American Society of Plant Biologists. All rights reserved.