Submitted to: PLoS Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2010
Publication Date: 11/11/2010
Citation: Baxter, I.R., Brazelton, J., Yu, D., Huang, Y., Lahner, B., Nordborg, M., Vitek, O., Salt, D.E. 2010. A coastal cline in sodium accumulation Arabidopsis thaliana is driven by natural variation of the sodium transporter AtHKT1;1. PLoS Genetics. 6(11). Available: http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1001193. Interpretive Summary: In order to grow in soils across the world, plants have adapted to tolerate a wide variety of different soil environments. Understanding the genetic mechanisms that have allowed wild plants to grow on sub-optimal environments will enable the development of improved crops that can withstand these environements. High levels of sodium (Na) are a major limitation on crop production worldwide. To identify genes that control Na accumulation in plant leaves we analyzed the levels of Na from accessions of a model plant, the wild mustard Arabidopsis Thaliana, that were collected from around the world. By combining this data with high-density genetic information on the lines we were able to identify a gene which transports Na across membranes as a major driver of Na accumulation. One version of this gene allows plants to accumulate up to five times more Na than plants with other versions of the gene. Previously it was shown that this version of the gene allows plants to tolerate higher levels of Na in the soil. Interestingly, this version of the gene appears to be expressed at lower levels than other versions of the gene, which we confirmed in our study population. When we looked at the geographic distribution of the collection sites of the lines which carried the high Na/Na tolerant version of the gene, we found that they were significantly more likely to have been collected near high Na containing soils or near the coast, where sea water might be increasing the Na levels of the soil. This suggests that this allele has allowed plants to adapt to the high Na soil environments. Understanding how this allele works could allow for the production of crop plants that can withstand high Na environments, thereby increasing productivity.
Technical 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. We used genome-wide association mapping to identify the sodium transporter AtHKT1;1 as a major locus controlling leaf sodium 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 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.