A coastal cline in sodium accumulation in Arabidopsis thaliana is driven by natural variation of the sodium transporter AtHKT1;1.

Ivan Baxter,Yu S Huang,Brett Lahner,Olga Vitek,Joy Bergelson,Magnus Nordborg,Danni Yu,David E Salt,Jessica N Brazelton,Yan Li,Justin O Borevitz,Elena Yakubova

doi:10.1371/journal.pgen.1001193

Abstract

The genetic model plant Arabidopsis thaliana, like many plant species, experiences a range of edaphic conditions across its natural habitat. Such heterogeneity may drive local adaptation, though the molecular genetic basis remains elusive. Here, we describe a study in which we used genome-wide association mapping, genetic complementation, and gene expression studies to identify cis-regulatory expression level polymorphisms at the AtHKT1;1 locus, encoding a known sodium (Na+) transporter, as being a major factor controlling natural variation in leaf Na+ accumulation capacity across the global A. thaliana population. A weak allele of AtHKT1;1 that drives elevated leaf Na+ in this population has been previously linked to elevated salinity tolerance. Inspection of the geographical distribution of this allele revealed its significant enrichment in populations associated with the coast and saline soils in Europe. The fixation of this weak AtHKT1;1 allele in these populations is genetic evidence supporting local adaptation to these potentially saline impacted environments.

Highlights

Uncovering the genetic polymorphisms that underlie adaptation to environmental gradients is a critical goal in evolutionary biology, and will lead to a better understanding of both the types of genetic changes and the gene functions involved
With DNA sequencing, such puzzles have extended to the geographical distribution of genetic variation within a species
We explain one such puzzle in the European population of Arabidopsis thaliana, where we find that a version of a gene encoding for a sodium-transporter with reduced function is almost uniquely found in populations of this plant growing close to the coast or on known saline soils

Summary

Introduction

Uncovering the genetic polymorphisms that underlie adaptation to environmental gradients is a critical goal in evolutionary biology, and will lead to a better understanding of both the types of genetic changes and the gene functions involved. Such understanding will provide insight into how organisms may respond to future global climate change, but will provide tools for the development of agricultural systems and ecological services that are more resilient to such changes. While adaptation to high altitude in Peromyscus maniculatus (Deer mice) is associated with enhanced pulmonary O2 loading driven by alterations in a-globin and b-globin genes [4] These genetic changes are all associated with adaptation to variation in environmental factors that vary with latitude or altitude. Because of its relevance to crop production, salinity tolerance in plants has been studied intensively [14], and natural plant populations adapted to such conditions have provided an excellent

Author Summary

Findings

Materials and Methods