Abstract Rhizobium tropici establishes symbiosis with several leguminous species, inducing nitrogen fixing nodules. Communication between rhizobia and legumes starts when the flavonoids secreted by plant roots interact with the R. tropici NodD protein to recognize plant signaling molecules present in the rhizosphere and begin the nodulation process. Some studies in R. tropici CIAT 899 have demonstrated that the induction of nod genes by saline stress influences the formation of nodules in plant roots. The aim of this study was to analyze the proteome profile of R. tropici CIAT 899 to investigate the molecular response of the bacterium under apigenin (flavonoid) and salt stress induction. The bacterium was grown in TY medium, considered as the control condition (CC), and in the presence of apigenin (AC) and NaCl (SSC). Total proteins were extracted and analyzed by two-dimensional electrophoresis (2-DE) and the differential spots were identified by MALDI-TOF MS/MS. A total of 105 differentially abundant protein spots were observed, including 2 present only in CC, 2 exclusive to AC and 6 to SSC. A total of 73% of these protein spots were identified by mass spectrometry. Proteins involved in transport and cellular processes were mostly increased in AC:CC and AC:SSC comparison, while in SSC:CC, these proteins were mostly decreased. Under salt stress, the bacterium reduced the uptake of molecules and energy consumption, reducing the abundance of ABC transporter proteins. These proteins are crucial for bacterial adaptation in environmental conditions and can be important for the nodulation process.

中文翻译：

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热带根瘤菌 CIAT 899 对芹菜素和盐胁迫诱导的蛋白质组反应

摘要 热带根瘤菌与几种豆科植物共生，诱导固氮根瘤。当植物根部分泌的类黄酮与热带红杆菌 NodD 蛋白相互作用以识别根际中存在的植物信号分子并开始结瘤过程时，根瘤菌和豆科植物之间的交流就开始了。在 R. tropici CIAT 899 中的一些研究表明，盐胁迫对 nod 基因的诱导会影响植物根部根瘤的形成。本研究的目的是分析 R. tropici CIAT 899 的蛋白质组谱，以研究该细菌在芹菜素（类黄酮）和盐胁迫诱导下的分子反应。细菌在 TY 培养基中生长，被视为对照条件 (CC)，并且存在芹菜素 (AC) 和 NaCl (SSC)。提取总蛋白并通过二维电泳 (2-DE) 进行分析，并通过 MALDI-TOF MS/MS 鉴定差异点。共观察到 105 个差异丰富的蛋白质点，其中 2 个仅存在于 CC，2 个仅存在于 AC，6 个存在于 SSC。通过质谱法鉴定了总共 73% 的这些蛋白质点。在 AC:CC 和 AC:SSC 比较中，参与运输和细胞过程的蛋白质大多增加，而在 SSC:CC 中，这些蛋白质大多减少。在盐胁迫下，细菌减少了分子的摄取和能量消耗，从而降低了 ABC 转运蛋白的丰度。这些蛋白质对于细菌在环境条件下的适应至关重要，并且对结瘤过程也很重要。