Differential activity of plasma and vacuolar membrane transporters contributes to genotypic differences in salinity tolerance in a Halophyte Species, Chenopodium quinoa.

Edgar Bonales-Alatorre,Sergey Shabala,Sven-Erik Jacobsen,Fanrong Zeng,Zhong-Hua Chen,Igor Pottosin,Lana Shabala

doi:10.3390/ijms14059267

Abstract

Halophytes species can be used as a highly convenient model system to reveal key ionic and molecular mechanisms that confer salinity tolerance in plants. Earlier, we reported that quinoa (Chenopodium quinoa Willd.), a facultative C3 halophyte species, can efficiently control the activity of slow (SV) and fast (FV) tonoplast channels to match specific growth conditions by ensuring that most of accumulated Na+ is safely locked in the vacuole (Bonales-Alatorre et al. (2013) Plant Physiology). This work extends these finding by comparing the properties of tonoplast FV and SV channels in two quinoa genotypes contrasting in their salinity tolerance. The work is complemented by studies of the kinetics of net ion fluxes across the plasma membrane of quinoa leaf mesophyll tissue. Our results suggest that multiple mechanisms contribute towards genotypic differences in salinity tolerance in quinoa. These include: (i) a higher rate of Na+ exclusion from leaf mesophyll; (ii) maintenance of low cytosolic Na+ levels; (iii) better K+ retention in the leaf mesophyll; (iv) a high rate of H+ pumping, which increases the ability of mesophyll cells to restore their membrane potential; and (v) the ability to reduce the activity of SV and FV channels under saline conditions. These mechanisms appear to be highly orchestrated, thus enabling the remarkable overall salinity tolerance of quinoa species.

Highlights

The physiological and genetic complexity of salt tolerance significantly handicaps progress in breeding crops for this important trait [1]
The results are complemented by studies of the kinetics of net ion fluxes across the plasma membrane of quinoa leaf mesophyll tissue
Our results suggest that multiple and highly orchestrated ionic mechanisms contribute to salinity tolerance in quinoa and this determines the genotypic variability in this trait in the

Summary

Introduction

The physiological and genetic complexity of salt tolerance significantly handicaps progress in breeding crops for this important trait [1]. About 1% of land plants are capable of surviving under highly saline conditions, but benefit from the presence of substantial quantities of salt in the growth media [2,3] For most of these species, optimal growth is achieved at salinity levels ranging between 150 and 200 mM (e.g., Salicornia [4]; Atriplex [5]; quinoa [6]), while for others, the optimum salt level in the media can be as high as seawater, i.e., ~500 mM NaCl (Sarcocornia fruticose and Arthrocnemum macrostachyum; [7]). Halophytes are classified as Na+ includers, while most crops adopt a

Results

Discussion

Conclusion