Purpose

Alkaline salinity constrains crop yield. Previously, we observed local adaptation of Arabidopsis thaliana to saline-siliceous soils (pH ≤ 7) and to non-saline carbonate soils. However, no natural population of A. thaliana was localized on saline-alkaline soils. This suggests that salinity tolerance evolved on saline-siliceous soils may not confer tolerance to alkaline salinity. This hypothesis was explored by addressing physiological and molecular responses to alkaline salinity of A. thaliana that differ in tolerance to either non-alkaline salinity or carbonate.

Methods

A. thaliana native to saline-siliceous soils (high salinity, HS), non-saline carbonate soils (high alkalinity, HA), or soils with intermediate levels of these factors (medium saline-alkalinity, MSA) were cultivated in common gardens on saline-siliceous or saline-calcareous substrates. Hydroponics and irrigation experiments confirmed the phenotypes. The growth, mineral concentrations, proline content, osmotic potential, genetic variation distribution, and expression levels of selected genes involved in salinity and alkalinity tolerance were assessed.

Results

HS performed best on saline-siliceous soil and in hydroponics with salinity (pH 5.9). However, HS was more sensitive to saline-alkaline conditions than HA and MSA. The fitness under saline-alkaline conditions was ranked according to MSA > HA > HS. Under alkaline salinity, MSA best maintained ion homeostasis, osmotic balance, and higher expression levels of key genes involved in saline or alkaline tolerance (AHA1, root HKT1 and FRO2, and shoot NHX1 and IRT1).

Conclusion

In A. thaliana, salinity tolerance evolved on saline-siliceous soils does not provide tolerance to alkaline salinity. Plants native to intermediate conditions (MSA) have more plasticity to adapt to alkaline salinity than those locally adapted to these individual stress factors.

中文翻译：

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拟南芥在硅质土壤上的耐盐性进化并不赋予对盐碱钙质土壤的耐受性

目的

碱性盐度限制作物产量。以前，我们观察到拟南芥对盐碱硅质土壤（pH ≤ 7）和非盐碱碳酸盐土壤的局部适应性。然而，在盐碱土壤上没有拟南芥的自然种群。这表明在含盐硅质土壤上进化出的耐盐性可能不会赋予对碱性盐度的耐受性。这一假设是通过解决对拟南芥碱性盐度的生理和分子反应进行探索的，这些反应对非碱性盐度或碳酸盐的耐受性不同。

方法

拟南芥原产于盐碱硅质土壤（高盐度，HS）、非盐碱度碳酸盐土壤（高碱度，HA）或具有中等水平这些因素的土壤（中等盐碱度，MSA），在盐-硅质或盐-钙质底物。水培和灌溉实验证实了表型。评估了参与盐度和碱度耐受性的选定基因的生长、矿物质浓度、脯氨酸含量、渗透势、遗传变异分布和表达水平。

结果

HS 在含盐硅质土壤和含盐度（pH 5.9）的水培中表现最佳。然而，HS 比 HA 和 MSA 对盐碱条件更敏感。盐碱条件下的适应度按照 MSA > HA > HS 排序。在碱性盐度条件下，MSA 能最好地维持离子稳态、渗透平衡，以及与耐盐或耐碱有关的关键基因（AHA1、根HKT1和FRO2，以及地上部 NHX1 和 IRT1 ）的更高表达水平。

结论

在拟南芥中，盐碱硅土上进化的耐盐性不提供对碱性盐度的耐受性。中间条件 (MSA) 的原生植物比那些局部适应这些个体胁迫因素的植物具有更大的可塑性来适应碱性盐度。