Rhizobia are ecologically important, facultative plant-symbiotic microbes. In nature, there is a large variability in the association of rhizobial strains and host plants of the same species. Here, we evaluated whether plant and rhizobial genotypes influence the initial transcriptional response of rhizobium following perception of a host plant. RNA sequencing of the model rhizobium Sinorhizobium meliloti exposed to root exudates or luteolin (an inducer of nod genes, involved in the early steps of symbiotic interaction) was performed on a combination of three S. meliloti strains and three alfalfa varieties as host plants. The response to root exudates involved hundreds of changes in the rhizobium transcriptome. Of the differentially expressed genes, 35% were influenced by the strain genotype, 16% were influenced by the plant genotype, and 29% were influenced by strain-by-host plant genotype interactions. We also examined the response of a hybrid S. meliloti strain in which the symbiotic megaplasmid (∼20% of the genome) was mobilized between two of the above-mentioned strains. Dozens of genes were upregulated in the hybrid strain, indicative of nonadditive variation in the transcriptome. In conclusion, this study demonstrated that transcriptional responses of rhizobia upon perception of legumes are influenced by the genotypes of both symbiotic partners and their interaction, suggesting a wide spectrum of genetic determinants involved in the phenotypic variation of plant-rhizobium symbiosis.

中文翻译：

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植物-根瘤菌共生的启动过程中基因型-基因型相互作用的非加性转录组签名。

根瘤菌是具有重要生态意义的兼性植物共生微生物。在自然界中，相同物种的根瘤菌菌株和寄主植物之间的关联存在很大的差异。在这里，我们评估植物和根瘤菌的基因型是否影响宿主植物感知后根瘤菌的初始转录反应。暴露于根系分泌物或木犀草素（nod基因的诱导物，参与共生相互作用的早期过程）的模型根瘤菌根瘤菌根瘤菌的RNA测序是对三种根瘤菌进行的。株和三个苜蓿品种作为寄主植物。对根系分泌物的反应涉及根瘤菌转录组的数百种变化。在差异表达基因中，35％受菌株基因型影响，16％受植物基因型影响，29％受株间宿主植物基因型相互作用影响。我们还检查了杂交S. meliloti的反应其中共生大质粒（约占基因组的20％）在上述两种菌株之间动员的菌株。杂种菌株中数十个基因被上调，表明转录组中的非累加变化。总之，这项研究表明，根瘤菌对豆类植物的感知所产生的转录反应受共生伴侣的基因型及其相互作用的影响，这表明植物-根瘤菌共生的表型变异涉及广泛的遗传决定因素。