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Functional Plant Biology Functional Plant Biology Society
Plant function and evolutionary biology
RESEARCH ARTICLE

ZxNHX1 indirectly participates in controlling K+ homeostasis in the xerophyte Zygophyllum xanthoxylum

Tian-Ge Gao A , Cui-Min Ma A , Hui-Jun Yuan A B , Hai-Shuang Liu A , Qing Ma A , Timothy J. Flowers C and Suo-Min Wang https://orcid.org/0000-0003-0027-8822 A D
+ Author Affiliations
- Author Affiliations

A State Key Laboratory of Grassland Agro-ecosystems; Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture and Rural Affairs; College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730020, PR China.

B School of Life Science and Engineering, Lanzhou University of Technology, Lanzhou 730050, PR China.

C Department of Evolution Behaviour and Environment, School of Life Sciences, University of Sussex, Falmer, Brighton, Sussex BN1 9QG, UK.

D Corresponding author. Email: smwang@lzu.edu.cn

Functional Plant Biology - https://doi.org/10.1071/FP20185
Submitted: 24 June 2020  Accepted: 6 November 2020   Published online: 7 December 2020

Abstract

The succulent xerophyte Zygophyllum xanthoxylum (Bunge) Engl. can absorb Na+ from the soil as an osmoticum in order to resist osmotic stress. The tonoplast Na+/H+ antiporter ZxNHX1 is essential for maintaining the salt-accumulation characteristics of Z. xanthoxylum by compartmentalizing Na+ into vacuoles. Previous results revealed that the silencing of ZxNHX1 greatly decreased Na+ accumulation in Z. xanthoxylum under 50 mM NaCl due to the weakened compartmentalisation; in addition, K+ concentration also significantly reduced in ZxNHX1-RNAi lines. Yet, whether the reduction of K+ concentration was directly triggered by the silencing of ZxNHX1 remains unclear. In this study, the growth parameters and expression levels of ZxSOS1, ZxHKT1;1, ZxAKT1 and ZxSKOR were measured in wild-type and ZxNHX1-RNAi lines under control or –0.5 MPa osmotic stress. The results showed that the silencing of ZxNHX1 inhibited the plant growth, decreased Na+ concentration in leaves, reduced the transcript abundance of ZxSOS1 and dramatically increased that of ZxHKT1;1 in roots of Z. xanthoxylum under osmotic stress; whereas tissue K+ concentrations and the expression level of ZxSKOR displayed no significant variations, and the expression of ZxAKT1 were significantly reduced in ZxNHX1-RNAi lines under osmotic stress, compared with the wild type. These results suggest that in Z. xanthoxylum, ZxNHX1 can maintain the normal growth by compartmentalizing Na+ into vacuoles, and regulate the spatial distribution of Na+ indirectly by affecting the expressions of ZxSOS1 and ZxHKT1;1. Moreover, the silencing of ZxNHX1 is not the main reason that led to the reduction of K+ concentration in ZxNHX1-RNAi lines under 50 mM NaCl, and ZxNHX1 might be indirectly involved in regulating K+ homeostasis.

Keywords: K+ transport, Na+ transport, osmotic stress, succulent, xerophyte, ZxNHX1, Zygophyllum xanthoxylum.


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