Aims

Alkaline salt is one of the most devastating environmental factors limiting alfalfa productivity, however, the mechanisms underlying adaptation of alfalfa to alkaline remain unclear. Our aim is to investigate proteomic and metabolomic differences in growth and root of alfalfa under alkaline salt in Rhizobium-alfalfa symbiotic relationships.

Methods

Rhizobium-inoculated and non-inoculated alfalfa plants were treated with 200 mmol/L NaHCO₃ to investigate physiological, metabolic, and proteomic responses of root-nodule symbiosis under alkaline-induced stress, using an integrated approach combining metabolome and proteome analysis with measurements of physiological parameters.

Results

The improved tolerance to alkalinity was observed in RI-plants compared with NI-plants. RI-plants accumulated more proline and MDH, and had higher antioxidant activity and relatively high RWC but low MDA content and low Na⁺/K⁺ ratio. The stress-related genes (P5CS, GST13, H⁺-Ppase, NADP-Me, SDH, and CS) were actively upregulated in RI plants under alkaline stress. In RI-plants, damage caused by alkaline stress was mainly alleviated by decreasing oxidative damage, enhancing the organic acid and amino acid metabolic processes, and scavenging harmful ROS by activating the phenylpropanoid biosynthetic pathway.

Conclusions

We revealed distinct proteins and metabolites related to alkali tolerance in RI-plants compared to NI-plants. Alkali tolerance of rhizobia-inoculated alfalfa was enhanced by altered proteins and metabolic processes as well as decreased oxidative damage.

中文翻译：

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根瘤菌接种的苜蓿对碱的耐受性增强与蛋白质和代谢过程的改变以及氧化损伤的减少有关

目的

碱性盐是限制苜蓿生产力的最具有破坏性的环境因素之一，但是，苜蓿适应碱性的机制尚不清楚。我们的目的是研究在根瘤菌-苜蓿共生关系下碱性盐作用下苜蓿生长和根的蛋白质组学和代谢组学差异。

方法

根瘤菌共生的生理，代谢和蛋白质组学响应，采用代谢组学和蛋白质组学分析相结合的综合方法，用200 mmol / L NaHCO ₃处理根瘤菌接种和未接种的苜蓿植物生理参数。

结果

与NI植物相比，在RI植物中观察到对碱度的改善的耐受性。RI植物积累更多的脯氨酸和MDH，具有较高的抗氧化活性和较高的RWC，但MDA含量低，Na ⁺ / K ⁺比低。在碱性胁迫下，RI植物中与胁迫相关的基因（P5CS，GST13，H ⁺ -Ppase，NADP-Me，SDH和CS）被积极上调。在RI植物中，碱性胁迫引起的损害主要是通过减少氧化损害，增强有机酸和氨基酸代谢过程以及通过激活苯丙烷类生物合成途径清除有害的ROS来减轻的。

结论

我们发现与NI植物相比，RI植物的耐碱性与蛋白质和代谢物有关。改变蛋白和代谢过程以及减少氧化损伤，可以增强接种根瘤菌的苜蓿的碱耐受性。