Project description:It is well-known that individual pea (Pisum sativum L.) cultivars differ in their symbiotic responsivity. This trait is typically manifested with an increase in seed weights due to inoculation with rhizobial bacteria and arbuscular mycorrhizal fungi. The aim of this work was to characterize the alterations in root proteome of highly responsive pea genotype k-8274 and low-responsive genotype k-3358 grown in non-sterile soil, which were associated with root colonization with rhizobial bacteria and arbuscular mycorrhiza fungi in comparison to proteome shifts caused by soil supplementation with mineral nitrogen salts. Our results clearly indicate that supplementation of the soil with mineral nitrogen-containing salts switched the root proteome of both genotypes to assimilation of the available nitrogen, whereas the processes associated with nitrogen fixation were suppressed. Surprisingly, inoculation with rhizobial bacteria had only a minor effect on root proteomes of the both genotypes. The most pronounced response was observed for highly responsive k-8274 genotype inoculated simultaneously with rhizobial bacteria and arbuscular mycorrhizal fungi. This response involved activation of the proteins related to redox metabolism and suppression of excessive nodule formation. In turn, the low-responsive genotype k-3358 demonstrated a pronounced inoculation-induced suppression of protein metabolism and enhanced diverse defense reactions in pea roots under the same soil conditions. The results of the study shed light on the molecular basis of differential symbiotic responsivity in different pea cultivars.
Project description:The study of orchid mycorrhizal interactions is particularly complex because of the peculiar life cycle of these plants and their diverse trophic strategies. Here, large-scale transcriptomics has been applied to investigate gene expression in the mycorrhizal roots of the terrestrial mixotrophic orchid Limodorum abortivum under natural conditions. Our results provide new insights into the mechanisms underlying plant-fungus interactions in orchids and in particular on the plant responses to the mycorrhizal symbiont(s) in adult roots. Comparison with gene expression in mycorrhizal roots of another orchid species, Oeceoclades maculata, suggests that amino acids may represent the main nitrogen source in both protocorms and adult orchids, at least for mixotrophic species. The upregulation, in mycorrhizal L. abortivum roots, of some symbiotic molecular marker genes identified in mycorrhizal roots from other orchids as well as in arbuscular mycorrhiza, suggests a common plant core of genes in endomycorrhizal symbioses. Further efforts will be required to understand whether the specificities of orchid mycorrhiza depend on fine-tuned regulation of these common components, or whether specific additional genes are involved.
Project description:Many plants associate with arbuscular mycorrhizal fungi for nutrient acquisition, while legumes also associate with nitrogen-fixing rhizobial bacteria. Both associations rely on symbiosis signaling and here we show that cereals can perceive lipochitooligosaccharides (LCOs) for activation of symbiosis signaling, surprisingly including Nod factors produced by nitrogen-fixing bacteria. However, legumes show stringent perception of specifically decorated LCOs, that is absent in cereals. LCO perception in plants is activated by nutrient starvation, through transcriptional regulation of Nodulation Signaling Pathway (NSP)1 and NSP2. These transcription factors induce expression of an LCO receptor and act through the control of strigolactone biosynthesis and the karrikin-like receptor DWARF14-LIKE. We conclude that LCO production and perception is coordinately regulated by nutrient starvation to promote engagement with mycorrhizal fungi. Our work has implications for the use of both mycorrhizal and rhizobial associations for sustainable productivity in cereals.
Project description:Nitrogen (N), the primary limiting factor for plant growth and yield in agriculture, has a patchy distribution in soils due to fertilizer application or decomposing organic matter. Studies in solution culture over-simplify the complex soil environment where microbial competition and spatial and temporal heterogeneity challenge roots’ ability to acquire adequate amounts of nutrients required for plant growth. In this study, various ammonium treatments (as 15N) were applied to a discrete volume of soil containing tomato (Solanum lycopersicum) roots to simulate encounters with a localized enriched patch of soil. Transcriptome analysis was used to identify genes differentially expressed in roots 53 hrs after treatment. Results: The ammonium treatments resulted in significantly higher concentrations of both ammonium and nitrate in the patch soil. The plant roots and shoots exhibited increased levels of 15N over time, indicating a sustained response to the enriched environment. Root transcriptome analysis identified 585 genes differentially regulated 53 hrs after the treatments. Nitrogen metabolism and cell growth genes were induced by the high ammonium (65 ug NH4+-N g-1 soil), while stress response genes were repressed. The complex regulation of specific transporters following the ammonium pulse reflects a simultaneous and synergistic response to rapidly changing concentrations of both forms of inorganic N in the soil patch. Transcriptional analysis of the phosphate transporters demonstrates cross-talk between N and phosphate uptake pathways and suggests that roots increase phosphate uptake via the arbuscular mycorrhizal symbiosis in response to N. Conclusion: This work enhances our understanding of root function by providing a snapshot of the response of the tomato root transcriptome to a pulse of ammonium in a complex soil environment. This response includes an important role for the mycorrhizal symbiosis in the utilization of an N patch.
Project description:The transcription factor regulatory network (TRN) in Pseudomonas aeruginosa is complicated and involves multiple regulators responding to various environmental signals and physiological cues by regulating gene expression. P. aeruginosa utilizes versatile virulent determinants to exert its virulence, including biofilm formation, quorum sensing (QS), Type III (T3SS) and Type IV (T6SS) secretion system, motility, siderophore production, oxidative stress resistance, and antibiotic resistance, which under the control of TRN. Herein, ChIP-seq was applied to investigate the binding sites of 158 TFs in P. aeruginosa PAO1 strain. The results revealed a total of 30,481 significant binding peaks in the genome, more than half of which were located in the promoter regions. To furthermore decode diverse regulatory relationships among TFs, the hierarchical network was assembled into three levels: top, middle, and bottom. Thirteen ternary regulatory motifs revealed flexible relations of TFs in small hubs, and a comprehensive co-association atlas was established and enriched three high-associated clusters. A total of 32 TFs were identified as master regulators in regulating virulence-related pathways, and 34 TFs were involved in four metabolism pathways significantly. These results will provide significant insight into understanding the pathogenesis mechanisms of P. aeruginosa and relevant bacteria and contributing to developing effective therapies for diseases caused by infection.
Project description:The transcription factor regulatory network (TRN) in Pseudomonas aeruginosa is complicated and involves multiple regulators responding to various environmental signals and physiological cues by regulating gene expression. P. aeruginosa utilizes versatile virulent determinants to exert its virulence, including biofilm formation, quorum sensing (QS), Type III (T3SS) and Type IV (T6SS) secretion system, motility, siderophore production, oxidative stress resistance, and antibiotic resistance, which under the control of TRN. Herein, ChIP-seq was applied to investigate the binding sites of 158 TFs in P. aeruginosa PAO1 strain. The results revealed a total of 30,481 significant binding peaks in the genome, more than half of which were located in the promoter regions. To furthermore decode diverse regulatory relationships among TFs, the hierarchical network was assembled into three levels: top, middle, and bottom. Thirteen ternary regulatory motifs revealed flexible relations of TFs in small hubs, and a comprehensive co-association atlas was established and enriched three high-associated clusters. A total of 32 TFs were identified as master regulators in regulating virulence-related pathways, and 34 TFs were involved in four metabolism pathways significantly. These results will provide significant insight into understanding the pathogenesis mechanisms of P. aeruginosa and relevant bacteria and contributing to developing effective therapies for diseases caused by infection.
Project description:Nitrogen (N), the primary limiting factor for plant growth and yield in agriculture, has a patchy distribution in soils due to fertilizer application or decomposing organic matter. Studies in solution culture over-simplify the complex soil environment where microbial competition and spatial and temporal heterogeneity challenge rootsâ ability to acquire adequate amounts of nutrients required for plant growth. In this study, various ammonium treatments (as 15N) were applied to a discrete volume of soil containing tomato (Solanum lycopersicum) roots to simulate encounters with a localized enriched patch of soil. Transcriptome analysis was used to identify genes differentially expressed in roots 53 hrs after treatment. Results: The ammonium treatments resulted in significantly higher concentrations of both ammonium and nitrate in the patch soil. The plant roots and shoots exhibited increased levels of 15N over time, indicating a sustained response to the enriched environment. Root transcriptome analysis identified 585 genes differentially regulated 53 hrs after the treatments. Nitrogen metabolism and cell growth genes were induced by the high ammonium (65 ug NH4+-N g-1 soil), while stress response genes were repressed. The complex regulation of specific transporters following the ammonium pulse reflects a simultaneous and synergistic response to rapidly changing concentrations of both forms of inorganic N in the soil patch. Transcriptional analysis of the phosphate transporters demonstrates cross-talk between N and phosphate uptake pathways and suggests that roots increase phosphate uptake via the arbuscular mycorrhizal symbiosis in response to N. Conclusion: This work enhances our understanding of root function by providing a snapshot of the response of the tomato root transcriptome to a pulse of ammonium in a complex soil environment. This response includes an important role for the mycorrhizal symbiosis in the utilization of an N patch. 9 Total samples were analyzed across 3 treatment groups (3 biological replicates per group). We generated the following pairwise comparisons using JMP Genomics software: Control vs. Low N, Control vs. high N, and low N vs. high N. One way ANOVA was used to determine significantly different expression. Genes with an FDRâ¤10% were presented.
Project description:Here we have compared adult wildtype (N2) C. elegans gene expression when grown on different bacterial environments/fod sources in an effort to model naturally occuring nematode-bacteria interactions at the Konza Prairie. We hypothesize that human-induced changes to natural environments, such as the addition of nitrogen fertalizer, have effects on the bacterial community in soils and this drives downstream changes in the structure on soil bacterial-feeding nematode community structure. Here we have used transcriptional profiling to identify candidate genes involved in the interaction of nematodes and bacteria in nature.