Project description:Plants and rhizosphere microbes rely closely on each other, with plants supplying carbon to bacteria in root exudates, and bacteria mobilizing soil-bound phosphate for plant nutrition. When the phosphate supply becomes limiting for plant growth, the composition of root exudation changes, affecting rhizosphere microbial communities and microbially-mediated nutrient fluxes. To evaluate how plant phosphate deprivation affects rhizosphere bacteria, Lolium perenne seedlings were root-inoculated with Pseudomonas aeruginosa 7NR, and grown in axenic microcosms under different phosphate regimes (330 uM vs 3-6 uM phosphate). The effect of biological nutrient limitation was examined by DNA microarray studies of rhizobacterial gene expression.
Project description: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.
Project description: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.
Project description: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.
Project description:The root-colonizing fungal endophyte Serendipita indica, formerly known as Piriformospora indica, is well known to promote plant biomass production and stress tolerance of its host plants. Co-cultivation of Arabidopsis thaliana seedlings with the fungus triggers a substantial induction of the growth of the root system. However, the molecular mechanisms by which the fungus promotes plant growth over an extended period of time is still unclear. We here report the comparative analysis of the effect of a mock- and S. indica-infection on wild-type Arabidopsis plants (Col-0) after 2 and 10 days of co-cultivation. Our data provide evidence for the induction of a number of genes that are consistingly induced during the plant–fungus interaction.
Project description:Flavonoids are stress-inducible metabolites important for plant-microbe interactions. In contrast to their well-known function in initiating rhizobia nodulation in legumes, it is unclear whether and how flavonoids may contribute to plant stress resistance through affecting non-nodulating bacteria in the root microbiome. Here we show how flavonoids preferentially attracts Aeromonadaceae in Arabidopsis thaliana root microbiome and how flavonoid-dependent recruitment of an Aeromona spp. results in enhanced plant Na_H1 resistance.
Project description:Flavonoids are stress-inducible metabolites important for plant-microbe interactions. In contrast to their well-known function in initiating rhizobia nodulation in legumes, it is unclear whether and how flavonoids may contribute to plant stress resistance through affecting non-nodulating bacteria in the root microbiome. Here we show how flavonoids preferentially attracts Aeromonadaceae in Arabidopsis thaliana root microbiome and how flavonoid-dependent recruitment of an Aeromona spp. results in enhanced plant drought resistance.
Project description:Pseudomonas fluorescens strain SS101 (Pf.SS101) promotes growth of Arabidopsis thaliana, enhances greening and lateral root formation, and induces systemic resistance (ISR) against the bacterial pathogen Pseudomonas syringae pv. tomato (Pst). Here, targeted and untargeted approaches were adopted to identify bacterial determinants and underlying mechanisms involved in plant growth promotion and ISR by Pf.SS101. Based on targeted analyses, no evidence was found for volatiles, lipopeptides and siderophores in plant growth promotion by Pf.SS101. Untargeted, genome-wide analyses of 7,488 random transposon mutants of Pf.SS101 led to the identification of 21 mutants defective in both plant growth promotion and ISR. Many of these mutants, however, were auxotrophic and impaired in root colonization. Genetic analysis of three mutants followed by site-directed mutagenesis, genetic complementation and plant bioassays revealed the involvement of the phosphogluconate dehydratase gene edd, the response regulator gene colR and the adenylsulfate reductase gene cysH in both plant growth promotion and ISR. Subsequent comparative plant transcriptomics analyses strongly suggest that modulation of sulfur assimilation, auxin biosynthesis and transport, steroid biosynthesis and carbohydrate metabolism in Arabidopsis are key mechanisms linked to growth promotion and ISR by Pf.SS101. Comparative transcriptome analysis of Arabidopsis treated with Pf. SS101, a growth and ISR promoting rhizobacteria and plants treated with cysH mutant of Pf.SS101 that fails to induce the afformentioned phenotypes
Project description:The root-colonizing fungal endophyte Serendipita indica, formerly known as Piriformospora indica, is well known to promote plant biomass production and stress tolerance of its host plants. Moreover, previous studies highlighted an important impact of the fungus on auxin homeostasis during the infection of Arabidopsis thaliana plants. Auxin is a key determinant of plant growth, including the growth of the root system. Auxin overproducing mutants, like for instance YUC9oe (Hentrich et al., 2013 Plant J.), show a pronounced root phenotype that can be restored by the co-cultivation with S. indica. We here report the comparative analysis of the effect of a mock- and S. indica-infection on both wild-type Arabidopsis plants (Col-0) and YUC9 overexpressing mutants. Our data provide evidence for the induction of GRETCHEN HAGEN 3 (GH3) genes that are involved in conjugating active free indole-3-acetic acid with amino acids. The fungus triggered induction GH3s is suggested to be involved in affecting the cellular auxin homeostasis.