Barley sodium content is regulated by natural variants of the Na+ transporter HvHKT1;5

Kelly Houston,Yue Qu,Pauline Smith,Matt Gilliham,Stefanie Wege,Maria Hrmova,Micha Bayer,Malcolm Macaulay,Miriam Schreiber,Paulina Flis,Stuart Roy,Apriadi Situmorang,Jiaen Qiu,Claire Halpin,David E Salt,Robbie Waugh,Caitlin Byrt,Helena Oakey,Joanne Russell

doi:10.1038/s42003-020-0990-5

Abstract

During plant growth, sodium (Na+) in the soil is transported via the xylem from the root to the shoot. While excess Na+ is toxic to most plants, non-toxic concentrations have been shown to improve crop yields under certain conditions, such as when soil K+ is low. We quantified grain Na+ across a barley genome-wide association study panel grown under non-saline conditions and identified variants of a Class 1 HIGH-AFFINITY-POTASSIUM-TRANSPORTER (HvHKT1;5)-encoding gene responsible for Na+ content variation under these conditions. A leucine to proline substitution at position 189 (L189P) in HvHKT1;5 disturbs its characteristic plasma membrane localisation and disrupts Na+ transport. Under low and moderate soil Na+, genotypes containing HvHKT1:5P189 accumulate high concentrations of Na+ but exhibit no evidence of toxicity. As the frequency of HvHKT1:5P189 increases significantly in cultivated European germplasm, we cautiously speculate that this non-functional variant may enhance yield potential in non-saline environments, possibly by offsetting limitations of low available K+.

Highlights

IntroductionSodium (Na+) in the soil is transported via the xylem from the root to the shoot
During plant growth, sodium (Na+) in the soil is transported via the xylem from the root to the shoot
We used Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to quantify sodium (Na+) and potassium (K+) content of wholegrain samples from five biological and five technical replicates of a small barley genome-wide association study (GWAS) panel comprised of 131 elite two-row spring genotypes

Summary

Introduction

Sodium (Na+) in the soil is transported via the xylem from the root to the shoot. Extensive historical evidence supports a requirement for nontoxic concentrations of Na+ to achieve maximal biomass growth in a wide range of plants[11] As such it has been suggested that Na+ is a functional nutrient, proposed to be capable of substituting for many of the essential roles that K+ ions play in plant nutrition including osmoregulation and enzyme activation[1]. Despite the reported positive attributes of Na+, by far the majority of studies in the more recent literature focus on the negative impacts of Na+ (i.e. salinity) on plant growth[12,13] These latter investigations generally seek to explore the possible mechanisms that explain how tolerance to excess Na+ can be achieved. Our data lead us to speculate, cautiously, that high Na+ accumulation may be a positive trait in the nonsaline conditions typical of high production agricultural environments

Methods

Results

Conclusion