BioProject

Plants develop mutualistic association with beneficial rhizobacteria. To understand this important phenomenon, early mechanisms for establishing the mutualism are critical. More...

Plants develop mutualistic association with beneficial rhizobacteria. To understand this important phenomenon, early mechanisms for establishing the mutualism are critical. Here we report that active DNA demethylation in plants controls root secretion of myo-inositol, which triggers and further facilitates colonization of the beneficial rhizobacteria Bacillus megaterium strain YC4, thereby allowing for plant growth-promotion. YC4 promotes plant growth but the beneficial effects were lost in the Arabidopsis mutant rdd that is defective in active DNA demethylation. Roots of rdd failed to associate with YC4, meanwhile the level of myo-inositol in root exudates was drastically reduced in rdd. Supplementation of myo-inositol to rdd restored YC4 colonization and plant growth-promotion, while plants with defective myo-inositol monophosphatase also failed in establishing mutualism with YC4. myo-Inositol not only induced chemotaxis of YC4 but also increased YC4 biofilm production, consistent with the transcriptional regulation of YC4 by myo-inositol. In addition, myo-inositol preferentially attracts Bacillus megaterium among the examined bacteria species. Regardless of YC4 inoculation, myo-inositol biosynthesis and catabolism genes are down- and up-regulated, respectively, in rdd compared to wild type plants. The differential expression of myo-inositol homeostasis genes is correlated with local DNA hypermethylation, whereas genetic disruption of the RNA-directed DNA methylation pathway abolished these epigenetic marks and reset the corresponding gene expression patterns, resulting in restored YC4 colonization and plant growth-promotion. Importantly, that active DNA demethylation controls myo-inositol-mediated mutualism between YC4 and plants was also demonstrated in Solanum lycopersicum. Our results uncover an important function of myo-inositol in plant-microbe interactions and its dependence on plant epigenetic regulation. Overall design: MethylC-Seq:4 samples examined, Col-0_M (mock), Col-0_T (treated), rdd_M, rdd_T(each sample has 2 replicates); Arabidopsis mRNA seq: 4 samples examined, Col-0_M(mock), Col-0_T(treated),rdd_M, rdd_T (each sample has 3 biological replicates); YC4-R4 bacteria mRNAseq: 2 samples examined, 6H_C (mock), 6H_T (treated)(each sample has 3 replicates) Less...