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;1^HLS) 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;1^HLS alleles correlates with soil sodium level over time, HKT1;1^HLS-harboring plants are better adapted to intermediate levels of salinity, and the HKT1;1^HLS 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.

土壤盐分和脱水等胁迫因素是植物生长的主要限制因素，导致全球范围内的农作物损失。使这些侮辱更加严重的是，不断增加的气候波动性要求适应不断变化的条件。拟南芥对盐分胁迫反应的了解相对较好，这使得该系统适合于进化机制的快速分子解剖。在加泰罗尼亚拟南芥的大规模基因组分析中，我们对沿海岸多个盐度梯度的77个个体进行了重新排序，并将这些数据与全球1,135个拟南芥进行了整合基因组的详细了解自然进化的盐度耐受性的人口统计和进化动力学。这表明适应高度变化的土壤盐度的加泰罗尼亚品种不是伊比利亚遗物，而是最近移居该地区。高亲和力K ⁺转运蛋白（HKT1; 1）基因座的三个等位基因变体的从头基因组组装解决了功能不同的等位基因之间的结构变异，这些等位基因响应土壤盐分的季节性变化而经历波动选择。携带等位基因的植物导致HKT1; 1的低根表达并因此导致高叶钠（HKT1; 1 ^HLS）是专门因地理和​​降雨变化而迁移到土壤钠含量波动较大的地区的移民。我们表明，植物的比例窝藏HKT1; 1 ^HLS等位基因水平土壤钠随时间相关，HKT1; 1个^HLS -harboring植物更好地适应盐度的中间水平，并且HKT1; 1个^HLS等位基因与累加器高钠簇全世界的加入。总之，我们的证据表明，HKT1; 1在应对气候波动的选择中处于波动之中，并且是适应盐碱条件的全球决定因素。