Project description:Microbes play key roles in diverse biogeochemical processes including nutrient cycling. However, responses of soil microbial community at the functional gene level to long-term fertilization, especially integrated fertilization (chemical combined with organic fertilization) remain unclear. Here we used microarray-based GeoChip techniques to explore the shifts of soil microbial functional community in a nutrient-poor paddy soil with long-term (21 years).The long-term fertilization experiment site (set up in 1990) was located in Taoyuan agro-ecosystem research station (28°55’N, 111°27’E), Chinese Academy of Sciences, Hunan Province, China, with a double-cropped rice system. fertilization at various regimes.
Project description:Soil transplant serves as a proxy to simulate climate change in realistic climate regimes. Here, we assessed the effects of climate warming and cooling on soil microbial communities, which are key drivers in Earth’s biogeochemical cycles, four years after soil transplant over large transects from northern (N site) to central (NC site) and southern China (NS site) and vice versa. Four years after soil transplant, soil nitrogen components, microbial biomass, community phylogenetic and functional structures were altered. Microbial functional diversity, measured by a metagenomic tool named GeoChip, and phylogenetic diversity are increased with temperature, while microbial biomass were similar or decreased. Nevertheless, the effects of climate change was overridden by maize cropping, underscoring the need to disentangle them in research. Mantel tests and canonical correspondence analysis (CCA) demonstrated that vegetation, climatic factors (e.g., temperature and precipitation), soil nitrogen components and CO2 efflux were significantly correlated to the microbial community composition. Further investigation unveiled strong correlations between carbon cycling genes and CO2 efflux in bare soil but not cropped soil, and between nitrogen cycling genes and nitrification, which provides mechanistic understanding of these microbe-mediated processes and empowers an interesting possibility of incorporating bacterial gene abundance in greenhouse gas emission modeling.
Project description:Most dairy cows suffer uterine microbial contamination postpartum. Persistent endometritis often develops, associated with reduced fertility. We used a model of differential feeding and milking regimes to produce cows in differing negative energy balance (NEB) status in early lactation. We used Affymetrix GeneChipÒ Bovine Genome Array to investigate the global gene expression underlying negative energy balance and to identify the significantly differentially expressed genes during this process.
Project description:Managing tradeoffs through gene regulation is believed to maintain resilience of a microbial community in a fluctuating resource environment. To investigate this hypothesis we imposed a fluctuating environment that required the sulfate-reducing generalist Desulfovibrio vulgaris to manage tradeoffs associated with repeated ecologically-relevant shifts between retaining metabolic independence (active capacity for sulfate respiration) and becoming metabolically specialized to a mutualistic association with the hydrogen consuming Methanococcus maripaludis. Strikingly, the microbial community became progressively less proficient at restoring the environmentally-relevant physiological state after each perturbation. Most cultures collapsed within 3-7 shifts with only a few collapsing later. We demonstrate that the collapse was caused by conditional gene regulation, which drove precipitous decline in intracellular abundance of essential transcripts and proteins, imposing greater energetic burden of regulation to restore function in a fluctuating environment. The microbial community collapse was rescued by a single regulatory mutation that could then potentially serve as a stepping stone for further adaptive evolution in a variable resource environment. Co-culture strains of M. maripaludis wild type and either wild type or DVU0744::Tn5 mutant of D. vulgaris strains were grown anaerobically in replicates. Samples were transitioned between syntrophic and sulfate respiratory growth conditions at early log phases.
Project description:The experiment at three long-term agricultural experimental stations (namely the N, M and S sites) across northeast to southeast China was setup and operated by the Institute of Soil Science, Chinese Academy of Sciences. This experiment belongs to an integrated project (The Soil Reciprocal Transplant Experiment, SRTE) which serves as a platform for a number of studies evaluating climate and cropping effects on soil microbial diversity and its agro-ecosystem functioning. Soil transplant serves as a proxy to simulate climate change in realistic climate regimes. Here, we assessed the effects of soil type, soil transplant and landuse changes on soil microbial communities, which are key drivers in Earth’s biogeochemical cycles.
Project description:Managing tradeoffs through gene regulation is believed to maintain resilience of a microbial community in a fluctuating resource environment. To investigate this hypothesis we imposed a fluctuating environment that required the sulfate-reducing generalist Desulfovibrio vulgaris to manage tradeoffs associated with repeated ecologically-relevant shifts between retaining metabolic independence (active capacity for sulfate respiration) and becoming metabolically specialized to a mutualistic association with the hydrogen consuming Methanococcus maripaludis. Strikingly, the microbial community became progressively less proficient at restoring the environmentally-relevant physiological state after each perturbation. Most cultures collapsed within 3-7 shifts with only a few collapsing later. We demonstrate that the collapse was caused by conditional gene regulation, which drove precipitous decline in intracellular abundance of essential transcripts and proteins, imposing greater energetic burden of regulation to restore function in a fluctuating environment. The microbial community collapse was rescued by a single regulatory mutation that could then potentially serve as a stepping stone for further adaptive evolution in a variable resource environment.
Project description:Studies investigating crop resistance to biotic and abiotic stress have largely focused on plant responses to singular forms of stress and individual biochemical pathways that only partially represent stress responses. Thus, combined biotic and abiotic stress treatments and the global assessment of their elicited metabolic expression remains largely unexplored. In this study, we employed targeted and untargeted metabolomics to investigate the metabolic responses of maize (Zea mays) to both individual and combinatorial stress treatments using heat (abiotic) and Cochliobolus heterostrophus infection (biotic) experiments. Ultra-high-performance liquid chromatography-high-resolution mass spectrometry revealed significant metabolic responses to C. heterostrophus infection and heat stress, and comparative analyses between these individual forms of stress demonstrated differential elicitation between the two global metabolomes. In combinatorial experiments, treatment with heat stress prior to fungal inoculation negatively impacted maize disease resistance against C. heterostrophus, and distinct metabolome separation between combinatorial stressed plants and the non-heat stressed infected controls was observed. Targeted analysis revealed inducible primary and secondary metabolite responses to biotic/abiotic stress, and combinatorial experiments indicated that deficiency in the hydroxycinnamic acid, p-coumaric acid, may lead to the heat-induced susceptibility of maize to C. heterostrophus. Collectively, these findings demonstrate that abiotic stress can predispose crops to more severe disease symptoms, underlining the increasing need to investigate defense chemistry in plants under combinatorial stress.
Project description:In the absence of adaptive immunity displayed by animals, plants respond locally to biotic challenge via inducible basal defense networks activated through recognition and response toconserved pathogen associated molecular patterns (PAMPs). In addition, immunity can be induced in tissues remote from infection sites via systemic acquired resistance (SAR), initiated following gene-for-gene recognition between plant resistance proteins and microbial effectors.The nature of the mobile signal and remotely activated networks responsible for establishing SAR remain unclear. Here we show that despite the absence of PAMP contact, systemically responding leaves rapidly activate a SAR transcriptional signature with strong similarity to local basal defense. Jasmonates have previously been implicated in systemic signalling in response to wounding and plant herbivory but not SAR. We present several lines of evidence that suggest jasmonates may also be central to SAR. Jasmonic acid (JA) rapidly accumulates in phloem exudates of leaves challenged with an avirulent strain of Pseudomonas syringae. In systemically responding leaves transcripts associated with jasmonate biosynthesis are upregulated and JA increases transiently. SAR can be mimicked by foliar JA application and is abrogated in mutants impaired in jasmonate synthesis or response. We conclude that, jasmonate signalling appears to mediate long-distance information transmission. Moreover, the systemic transcriptional response shares extraordinary overlap with local herbivory and wounding responses, indicating that jasmonates may be central to an evolutionarily conserved signalling network, which decodes multiple abiotic and biotic stress signals. Experimenter name: William Truman; Experimenter phone: +44 (0)1392 263789; Experimenter fax: +44 (0)1392 263434; Experimenter address: School of Biosciences; Experimenter address: Geoffrey Pope Building; Experimenter address: Stocker Road; Experimenter address: Exeter; Experimenter address: Devon; Experimenter zip/postal_code: EX4 4QD; Experimenter country: UK Experiment Overall Design: 9 samples were used in this experiment
Project description:Most dairy cows suffer uterine microbial contamination postpartum. Persistent endometritis often develops, associated with reduced fertility. We used a model of differential feeding and milking regimes to produce cows in differing negative energy balance (NEB) status in early lactation. We used Affymetrix GeneChipM-CM-^R Bovine Genome Array to investigate the global gene expression underlying negative energy balance and to identify the significantly differentially expressed genes during this process. We investigate the differences of gene expression profiles in uterine endometrial tissues between the cows with mild and severe negative energy balance.
Project description:Plants are often challenged by numerous biotic and abiotic environmental stresses. They have evolved efficient signaling networks in response to the environmental challenges, such as pathogen invasion, drought, CO2 changes. Guard cells are specialized epidermal cells enclosing pores on leaf surface, aka, stomata. Stomatal guard cells are at the frontline of biotic and abiotic stress responses. The opening and closing of stomata are regulated by a sophisticated intracellular signaling networks. Mitogen-activated protein kinase 4 (MPK4) was first identified as negative regulator in systemic acquired resistance (SAR). It was also play important roles in cytokinesis, reproduction, and photosynthesis. MPK4 has higher expression levels in plant guard cells than in mesophyll cells. Arabidopsis mpk4 mutant has higher levels of salicylic acid (SA) and reactive oxygen species (ROS), which are related with stomatal movement. The specific function of MPK4 in guard cells is unknown. In order to understand MPK4 functions in guard cells, it is essential to investigate MPK4-associated protein complex. Here we focus on identification of guard cell specific MPK4 complex using affinity purification following by mass spectrometry (AP-MS). Potential substrates were selected and validated with yeast two hybrid (Y2H).