Project description:The presence of genetic groups of the entomopathogenic fungus Metarhizium anisopliae in soil is shaped by its adaptability to specific soil and habitat types, and by soil insect populations. Although the entomopathogenic life style of this fungus is well studied, its saprophytic life style has received little consideration. While a set of functionally related genes can be commonly expressed for the adaptability of this fungus to different environments (insect cuticle, insect blood and root exudates), a different subset of genes is also expected for each environment. In order to increase the knowledge of the potential use of M. anisopliae as a rhizosphere competent organism, in this study we evaluated the genetic expression of this fungus while growing on plant root exudates in laboratory conditions during a time course.
Project description:Arsenic (As) bioavailability in the rice rhizosphere is influenced by many microbial interactions, particularly by metal-transforming functional groups at the root-soil interface. This study was conducted to examine As-transforming microbes and As-speciation in the rice rhizosphere compartments, in response to two different water management practices (continuous and intermittently flooded), established on fields with high to low soil-As concentration. Microbial functional gene composition in the rhizosphere and root-plaque compartments were characterized using the GeoChip 4.0 microarray. Arsenic speciation and concentrations were analyzed in the rhizosphere soil, root-plaque, porewater and grain samples. Results indicated that intermittent flooding significantly altered As-speciation in the rhizosphere, and reduced methyl-As and AsIII concentrations in the pore water, root-plaque and rice grain. Ordination and taxonomic analysis of detected gene-probes indicated that root-plaque and rhizosphere assembled significantly different metal-transforming functional groups. Taxonomic non-redundancy was evident, suggesting that As-reduction, -oxidation and -methylation processes were performed by different microbial groups. As-transformation was coupled to different biogeochemical cycling processes establishing functional non-redundancy of rice-rhizosphere microbiome in response to both rhizosphere compartmentalization and experimental treatments. This study confirmed diverse As-biotransformation at root-soil interface and provided novel insights on their responses to water management, which can be applied for mitigating As-bioavailability and accumulation in rice grains.
Project description:The presence of genetic groups of the entomopathogenic fungus Metarhizium anisopliae in soil is shaped by its adaptability to specific soil and habitat types, and by soil insect populations. Although the entomopathogenic life style of this fungus is well studied, its saprophytic life style has received little consideration. While a set of functionally related genes can be commonly expressed for the adaptability of this fungus to different environments (insect cuticle, insect blood and root exudates), a different subset of genes is also expected for each environment. In order to increase the knowledge of the potential use of M. anisopliae as a rhizosphere competent organism, in this study we evaluated the genetic expression of this fungus while growing on plant root exudates in laboratory conditions during a time course. One fungal strain: Metarhizium anisopliae ARSEF 2575; Five time conditions: 0h, 1h, 4h, 8h, 12h; Five-condition experiment: Time0h vs. Time1h, Time1h vs. Time4h, Time4h vs. Time8h, Time8h vs. Time12h and Time12h vs. Time0h. Two Biological replicates: independently grown and harvested. Three replicates per array. Dye-swap was performed on replicate 2.
Project description:Plants coexist in close proximity with numerous microorganisms in their rhizosphere. With certain microorganisms, plants establish mutualistic relationships that can confer physiological benefits to the interacting organisms, including enhanced nutrient assimilation or increased stress tolerance. The root-colonizing endophytic fungi Penicillium chrysogenum, Penicillium minioluteum, and Serendipita indica have been reported to enhance the drought stress tolerance of plants. However, to date, the molecular mechanisms triggered by these fungi in plants remain unexplored. This study presents a comparative analysis of the effects on mock- and fungus-infected tomato plants (var. Moneymaker) under drought stress conditions (40% field capacity) and control conditions (100% field capacity). The findings provide evidence for the induction of common response modules by the fungi.
Project description:Background: The soil environment is responsible for sustaining most terrestrial plant life on earth, yet we know surprisingly little about the important functions carried out by diverse microbial communities in soil. Soil microbes that inhabit the channels of decaying root systems, the detritusphere, are likely to be essential for plant growth and health, as these channels are the preferred locations of new root growth. Understanding the microbial metagenome of the detritusphere and how it responds to agricultural management such as crop rotations and soil tillage will be vital for improving global food production. Methods: The rhizosphere soils of wheat and chickpea growing under + and - decaying root were collected for metagenomics sequencing. A gene catalogue was established by de novo assembling metagenomic sequencing. Genes abundance was compared between bulk soil and rhizosphere soils under different treatments. Conclusions: The study describes the diversity and functional capacity of a high-quality soil microbial metagenome. The results demonstrate the contribution of the microbiome from decaying root in determining the metagenome of developing root systems, which is fundamental to plant growth, since roots preferentially inhabit previous root channels. Modifications in root microbial function through soil management, can ultimately govern plant health, productivity and food security.
Project description:Understanding the environmental factors that shape microbial communities is crucial, especially in extreme environments, like Antarctica. Two main forces were reported to influence Antarctic soil microbes: birds and plants. Both birds and plants are currently undergoing unprecedented changes in their distribution and abundance due to global warming. However, we need to clearly understand the relationship between plants, birds and soil microorganisms. We therefore collected rhizosphere and bulk soils from six different sampling sites subjected to different levels of bird influence and colonized by Colobanthus quitensis and Deschampsia antarctica in the Admiralty Bay, King George Island, Maritime Antarctic. Microarray and qPCR assays targeting 16S rRNA genes of specific taxa were used to assess microbial community structure, composition and abundance and analyzed with a range of soil physico-chemical parameters. The results indicated significant rhizosphere effects in four out of the six sites, including areas with different levels of bird influence. Acidobacteria were significantly more abundant in soils with little bird influence (low nitrogen) and in bulk soil. In contrast, Actinobacteria were significantly more abundant in the rhizosphere of both plant species. At two of the sampling sites under strong bird influence (penguin colonies), Firmicutes were significantly more abundant in D. antarctica rhizosphere but not in C. quitensis rhizosphere. The Firmicutes were also positively and significantly correlated to the nitrogen concentrations in the soil. We conclude that the microbial communities in Antarctic soils are driven both by bird and plants, and that the effect is taxa-specific.
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:Many of the microorganisms that are normally present in the soil, actually inhabit the rhizosphere and interact with plants. Those plant–microorganisms interactions may be beneficial or harmful. Among the first are the arbuscular mycorrhizal fungi (AMF). These soil fungi have been reported to improve plant resistance/tolerance to pests and diseases. On the other hand, soilborne pathogens represent a threat to agriculture generating important yield losses, depending upon the pathogen and the crop. One example is the “Sudden Death Syndrome” (SDS), a severe disease in soybean (Glycine max (L.) Merr) caused by a complex of at least four species of Fusarium sp., among which Fusarium virguliforme and F. tuccumaniae are the most prevalent in Argentina. This study provides, under strict in vitro culture conditions, a global analysis of transcript modifications in mycorrhizal and non-mycorrhizal soybean root associated with F. virguliforme inoculation. Microarray results showed qualitative and quantitative changes in the expression of defense-related genes in mycorrhizal soybean, suggesting that AMF are good candidates for sustainable plant protection against F. virguliforme.
Project description:Previously, we investigated the effect of fungal VOCs on the behavior of phylogenetically different soil bacteria (Schmidt et al 2015). In these experiments we showed that VOCs emitted by several fungi can lead to phenotypical responses in bacteria, for example, by inducing a change in motility (Schmidt et al 2015). We observed that the plant pathogenic fungus Fusarium culmorum produced a unique cluster of VOCs consisting primarily of terpenes. When exposed to the VOCs emitted by this fungus, the rhizobacterium Serratia plymuthica PRI-2C responded with an induction of motility. It is plausible that in soil, microorganisms sense changes in their environments via shifts in VOCs blend and adapt their behavior accordingly (Garbeva et al 2014). Although several studies indicated that VOCs can be used as signaling molecules in microbial inter-species interactions, the following questions remain unanswered as how are VOCs perceived as signals by the microorganisms and which regulatory pathways and genes are involved in the response? To answer these questions, the rhizosphere isolate S. plymuthica PRI-2C was grown alone or exposed to VOCs emitted by F. culmorum. The bacterial transcriptome and proteome were analyzed under each situation to identify the molecular basis of the bacterial response to fungal VOCs.
Project description:Elevated atmospheric CO2 can influence the structure and function of rhizosphere microorganisms by altering root growth and the quality and quantity of compounds released into the rhizosphere via root exudation. In these studies we investigated the transcriptional responses of Bradyrhizobium japonicum cells growing in the rhizosphere of soybean plants exposed to elevated atmospheric CO2. The results of microarray analyses indicated that atmospheric elevated CO2 concentration indirectly influences on expression of large number of Bradyrhizobium genes through soybean roots. In addition, genes involved in C1 metabolism, denitrification and FixK2-associated genes, including those involved in nitrogen fixation, microanaerobic respiration, respiratory nitrite reductase, and heme biosynthesis, were significantly up-regulated under conditions of elevated CO2 in the rhizosphere, relative to plants and bacteria grown under ambient CO2 growth conditions. The expression profile of genes involved in lipochitinoligosaccharide Nod factor biosynthesis and negative transcriptional regulators of nodulation genes, nolA and nodD2, were also influenced by plant growth under conditions of elevated CO2. Taken together, results of these studies indicate that growth of soybeans under conditions of elevated atmospheric CO2 influences gene expressions in B. japonicum in the soybean rhizosphere, resulting in changes to carbon/nitrogen metabolism, respiration, and nodulation efficiency.