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Fluctuating selection on migrant adaptive sodium transporter alleles in coastal Arabidopsis thaliana

Busoms, Silvia; Paajanen, Pirita; Marburger, Sarah; Bray, Sian; Huang, Xin-Yuan; Poschenrieder, Charlotte; Yant, Levi; Salt, David E.


Silvia Busoms

Pirita Paajanen

Sarah Marburger

Sian Bray

Xin-Yuan Huang

Charlotte Poschenrieder

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Professor of Evolutionary Genomics

David E. Salt


Stressors such as soil salinity and dehydration are major constraints on plant growth, causing worldwide crop losses. Compounding these insults, increasing climate volatility requires adaptation to fluctuating conditions. Salinity stress responses are relatively well understood in Arabidopsis thaliana, making this system suited for the rapid molecular dissection of evolutionary mechanisms. In a large-scale genomic analysis of Catalonian A. thaliana, we resequenced 77 individuals from multiple salinity gradients along the coast and integrated these data with 1,135 worldwide A. thaliana genomes for a detailed understanding of the demographic and evolutionary dynamics of naturally evolved salinity tolerance. This revealed that Catalonian varieties adapted to highly fluctuating soil salinity are not Iberian relicts but instead have immigrated to this region more recently. De novo genome assembly of three allelic variants of the high-affinity K+ transporter (HKT1;1) locus resolved structural variation between functionally distinct alleles undergoing fluctuating selection in response to seasonal changes in soil salinity. Plants harboring alleles responsible for low root expression of HKT1;1 and consequently high leaf sodium (HKT1;1HLS) were migrants that have moved specifically into areas where soil sodium levels fluctuate widely due to geography and rainfall variation. We demonstrate that the proportion of plants harboring HKT1;1HLS alleles correlates with soil sodium level over time, HKT1;1HLS-harboring plants are better adapted to intermediate levels of salinity, and the HKT1;1HLS allele clusters with high-sodium accumulator accessions worldwide. Together, our evidence suggests that HKT1;1 is under fluctuating selection in response to climate volatility and is a worldwide determinant in adaptation to saline conditions.


Busoms, S., Paajanen, P., Marburger, S., Bray, S., Huang, X., Poschenrieder, C., …Salt, D. E. (2018). Fluctuating selection on migrant adaptive sodium transporter alleles in coastal Arabidopsis thaliana. Proceedings of the National Academy of Sciences, 115(52), E12443-E12452.

Journal Article Type Article
Acceptance Date Nov 7, 2018
Online Publication Date Dec 7, 2018
Publication Date Dec 7, 2018
Deposit Date Dec 15, 2018
Publicly Available Date Dec 17, 2018
Journal Proceedings of the National Academy of Sciences
Print ISSN 0027-8424
Electronic ISSN 1091-6490
Publisher National Academy of Sciences
Peer Reviewed Peer Reviewed
Volume 115
Issue 52
Pages E12443-E12452
Public URL
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