Plant growth‐promoting rhizobacteria (PGPR), whose growth is stimulated by root exudates, are able to improve plant growth and health. Among those, bacteria of the genus Azospirillum were shown to affect root secondary metabolite content in rice and maize, sometimes without visible effects on root architecture. Transcriptomic studies also revealed that expression of several genes involved in stress and plant defense was affected, albeit with fewer genes when a strain was inoculated onto its original host cultivar. Here, we investigated, via a metabolic profiling approach, whether rice roots responded differently and with gradual intensity to various PGPR, isolated from rice or not. A common metabolomic signature of nine compounds was highlighted, with the reduced accumulation of three alkylresorcinols and increased accumulation of two hydroxycinnamic acid amides (HCAA), identified as N‐p‐coumaroylputrescine and N‐feruloylputrescine. This was accompanied by the increased transcription of two genes involved in the N‐feruloylputrescine biosynthetic pathway. Interestingly, exposure to a rice bacterial pathogen triggered a reduced accumulation of these HCAA in roots, a result contrasting with previous reports of increased HCAA content in leaves upon pathogen infection. Accumulation of HCAA, that are potential antimicrobial compounds, might be considered as a primary reaction of plant to bacterial perception.

中文翻译：

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接种各种根瘤菌后，可以观察到常见的代谢组学特征。

促进植物生长的根瘤菌（PGPR），其生长受到根系分泌物的刺激，能够改善植物的生长和健康。其中，偶氮螺旋菌属细菌被证明会影响水稻和玉米根系次生代谢产物的含量，有时对根系结构没有明显影响。转录组学研究还表明，将菌株接种到其原始宿主品种上后，与胁迫和植物防御相关的几个基因的表达受到影响，尽管其基因较少。在这里，我们通过代谢谱分析方法研究了水稻根部对从水稻中分离出来的各种PGPR的反应是否不同且逐渐增强。突出了九种化合物的常见代谢组学特征，减少了三种烷基间苯二酚的积累并增加了两种被鉴定为N - p-香豆酰putrescine和N的羟基肉桂酰胺（HCAA）的积累。阿魏酰putrescine。这伴随着参与N-阿魏酸酯生物素合成途径的两个基因转录的增加。有趣的是，暴露于水稻细菌病原体导致这些HCAA在根中的积累减少，这与先前报道的病原体感染后叶片中HCAA含量增加的报道形成了鲜明对比。HCAA的积累是潜在的抗菌化合物，可能被认为是植物对细菌感知的主要反应。