Data_Sheet_2_Root exudates and rhizosphere soil bacterial relationships of Nitraria tangutorum are linked to k-strategists bacterial community under salt stress.docx

When plants are subjected to various biotic and abiotic stresses, the root system responds actively by secreting different types and amounts of bioactive compounds, while affects the structure of rhizosphere soil bacterial community. Therefore, understanding plant–soil-microbial interactions, especially the strength of microbial interactions, mediated by root exudates is essential. A short-term experiment was conducted under drought and salt stress to investigate the interaction between root exudates and Nitraria tangutorum rhizosphere bacterial communities. We found that drought and salt stress increased rhizosphere soil pH (9.32 and 20.6%) and electrical conductivity (1.38 and 11 times), respectively, while decreased organic matter (27.48 and 31.38%), total carbon (34.55 and 29.95%), and total phosphorus (20 and 28.57%) content of N. tangutorum rhizosphere soil. Organic acids, growth hormones, and sugars were the main differential metabolites of N. tangutorum under drought and salt stress. Salt stress further changed the N. tangutorum rhizosphere soil bacterial community structure, markedly decreasing the relative abundance of Bacteroidota as r-strategist while increasing that of Alphaproteobacteria as k-strategists. The co-occurrence network analysis showed that drought and salt stress reduced the connectivity and complexity of the rhizosphere bacterial network. Soil physicochemical properties and root exudates in combination with salt stress affect bacterial strategies and interactions. Our study revealed the mechanism of plant–soil-microbial interactions under the influence of root exudates and provided new insights into the responses of bacterial communities to stressful environments.

当植物受到多种生物与非生物胁迫时，根系会主动分泌不同种类和含量的生物活性化合物，进而影响根际土壤细菌群落的结构。因此，解析由根系分泌物（root exudates）介导的植物-土壤-微生物互作（尤其是微生物互作强度）具有重要意义。本研究针对干旱与盐胁迫开展了短期试验，以探究根系分泌物与唐古特白刺（Nitraria tangutorum）根际细菌群落之间的互作关系。研究结果显示，干旱与盐胁迫分别使唐古特白刺根际土壤的酸碱度（pH）升高了9.32%与20.6%，电导率（electrical conductivity）分别升高了1.38倍与11倍；同时使该根际土壤的有机质（organic matter）、总碳（total carbon）与总磷（total phosphorus）含量分别下降了27.48%、31.38%，34.55%、29.95%，以及20%、28.57%。干旱与盐胁迫下，唐古特白刺的主要差异代谢物（differential metabolites）为有机酸、生长激素与糖类物质。盐胁迫进一步改变了唐古特白刺根际土壤的细菌群落结构，显著降低了作为r-策略者（r-strategist）的拟杆菌门（Bacteroidota）的相对丰度，同时提升了作为k-策略者（k-strategists）的α-变形菌纲（Alphaproteobacteria）的相对丰度。共现网络分析（co-occurrence network analysis）结果表明，干旱与盐胁迫降低了根际细菌网络的连通性与复杂度。土壤理化性质（soil physicochemical properties）与根系分泌物共同结合盐胁迫，会调控细菌的生存策略与互作关系。本研究揭示了根系分泌物介导下的植物-土壤-微生物互作机制，为解析细菌群落对胁迫环境的响应提供了新视角。