Gene expression data of Sinorhizobium meliloti-alfalfa initiation of symbiosis

Rhizobia are ecologically important, facultative plant symbiotic microbes.
In nature there exists 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 host plant. RNA-sequencing
of the model rhizobium Sinorhizobium meliloti exposed to root exudates or
luteolin was performed in a combination of three S. meliloti strains and
three Medicago sativa varieties. The response to root exudates involved
hundreds of changes in the rhizobium transcriptome. Of the differentially
expressed genes, expression of 35% were influenced by strain genotype, 16%
by the plant genotype, and 29% by strain x 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
up-regulated 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 is
influenced by the genotypes of both symbiotic partners, and their
interaction, a wide spectrum of genetic determinants involved in the
phenotypic variation of plant-rhizobium symbiosis.