Root exudates play a crucial role in the symbiosis between leguminous plants and rhizobia. Our previous studies have shown that a fungal endophyte Phomopsis liquidambaris promotes peanut-rhizobia nodulation and nitrogen fixation, but the underlying mechanism are largely unknown. Here, we explore the role of peanut root exudates in Ph. liquidambaris-mediated nodulation enhancement. We first collected root exudates from Ph. liquidambaris-inoculated and un-inoculated peanuts and determined their effects on rhizobial growth, biofilm formation, chemotaxis, nodC gene expression, and peanut nodulation. Our results found a positive effect of Ph. liquidambaris-inoculated root exudates on these characteristics of rhizobia. Next, we compared the root exudates profile of Ph. liquidambaris-inoculated and un-inoculated plants and found that Ph. liquidambaris altered the concentrations of phenolic acids, flavonoids, organic acids and amino acids in root exudates. Furthermore, the rhizobial chemotaxis, growth and biofilm formation in response to the changed compounds at different concentrations showed that all of the test compounds induced rhizobial chemotactic behavior, and organic acids (citric acid and oxalic acid) and amino acid (glutamate, glycine and glutamine) at higher concentrations increased rhizobial growth and biofilm formation. Collectively, our results suggest that root exudates alterations contribute to Ph. liquidambaris-mediated peanut-rhizobia nodulation enhancement.

根系分泌物在豆科植物和根瘤菌之间的共生中起着至关重要的作用。我们之前的研究表明，真菌内生菌Phomopsis liquidambaris促进花生根瘤菌的结瘤和固氮，但其潜在机制在很大程度上是未知的。在这里，我们探讨了花生根分泌物在Ph.liquidambaris介导的结瘤增强中的作用。我们首先从收集根分泌物pH值。liquidambaris -inoculated和未接种花生和确定它们对根瘤菌的生长，生物膜形成，趋化，效果NODC基因表达，和花生结瘤。我们的结果发现Ph.liquidambaris的积极作用- 在根瘤菌的这些特征上接种根系分泌物。接下来，我们比较了杜鹃花接种和未接种植物的根系分泌物谱，发现杜鹃花改变了根系分泌物中酚酸、黄酮类化合物、有机酸和氨基酸的浓度。此外，响应于不同浓度变化的化合物的根瘤菌趋化性、生长和生物膜形成表明，所有测试化合物均诱导根瘤菌趋化行为，有机酸（柠檬酸和草酸）和氨基酸（谷氨酸、甘氨酸和谷氨酰胺） ) 在较高浓度下会增加根瘤菌的生长和生物膜的形成。总的来说，我们的结果表明根系分泌物的改变有助于Ph.liquidambaris介导的花生根瘤菌结瘤增强。