Project description:Phosphorus (P) is an essential nutrient for plant growth and productivity. Due to soil fixation, however, phosphorus availability in soil is rarely sufficient to sustain high crop yields. Fertilizers are widely used to circumvent the limited bioavailability of phosphate (Pi) which led to a scenario of excessive soil P in agricultural soils. Whereas adaptive responses to Pi deficiency have been deeply studied, less is known about how plants adapt to Pi excess and how Pi excess might affect disease resistance. Here, we show that high Pi fertilization in rice plants, and subsequent Pi accumulation in leaves, enhances susceptibility to infection by Magnaporthe oryzae, the causal agent of the rice blast disease. Equally, MIR399f overexpression causes an increase in Pi content in rice leaves which results in enhanced susceptibility to M. oryzae. During pathogen infection, a weaker activation of defense-related genes occurs in rice plants accumulating Pi in leaves, a response that is in agreement with the phenotype of blast susceptibility observed in these plants. These data support that Pi, when in excess, compromises defense mechanisms in rice while demonstrating that miR399 functions as a negative regulator of rice immunity. The two signaling pathways, Pi signaling and defense signaling, must operate in a coordinated manner in controlling disease resistance. This information provides a basis to understand the molecular mechanisms involved in immunity in rice plants grown under a high Pi fertilization regime, an aspect that should be considered in management of the rice blast disease
Project description:We used the previously designed oligonucleotide microarrays (BM-CM-<rgmann et al., 2007, Environmental Microbiology, 9: 2742-2755) to detect the mRNA transcripts of R. pomeroyi DSS-3 when the cells were cultured under steady-state conditions limited with ammonium (NH4Cl, 0.26 mM) but with an excess of D-ribose-5-phosphate (C5H9Na2O8P*2H2O, 0.5 mM), methylphosphonic acid (CH5PO3, 0.5 mM), or potassium phosphate (KH2PO4, 0.5 mM), or during ammonium excess (NH4Cl, 2.8 mM) but were limited with potassium phosphate (KH2PO4, 9.2 M-NM-<M). A total of 13 microarray hybridizations were performed: three biological replicates each from ribose phosphate, methylphosphonate, or potassium phosphate excess growth regimes, three biological replicates from potassium phosphate limited growth regime, and one technical replicate for the potassium phosphate excess growth regime. Data for the technical replicates were averaged and combined, resulted in a total of 12 samples.
Project description:We used the previously designed oligonucleotide microarrays (Bürgmann et al., 2007, Environmental Microbiology, 9: 2742-2755) to detect the mRNA transcripts of R. pomeroyi DSS-3 when the cells were cultured under steady-state conditions limited with ammonium (NH4Cl, 0.26 mM) but with an excess of D-ribose-5-phosphate (C5H9Na2O8P*2H2O, 0.5 mM), methylphosphonic acid (CH5PO3, 0.5 mM), or potassium phosphate (KH2PO4, 0.5 mM), or during ammonium excess (NH4Cl, 2.8 mM) but were limited with potassium phosphate (KH2PO4, 9.2 μM).
Project description:Phosphorus is an essential macronutrient element, but some time causes problems if present in excess. Unlike the enormous molecular and morphophysiological information available in plants regarding phosphate (Pi) deficiency, little is known about the effect of excess Pi on plants, which is indeed essential for its remediation. Here, we have carried out a comparative study of plant molecular responses under excess Pi (20 mM) or without Pi (0 mM) at transcriptome level. The 1.25 mM treatment concentration of Pi used as a control to obtain differentially regulated genes under above mentioned Pi regimes. A novel whole-transcript expression array, i.e. Arabidopsis Gene 1.0 ST Array, was used to perform these experiments. The most distinctly regulated groups of genes represent modulation in ethylene mediated signaling, Fe deficiency response, and root development. We have also identified some defensin like genes, possessing a gibberellic acid regulated domain (GASA like) under excess Pi treatment. Overall, this study will not only help in dissecting the mechanism of plant responses under excess Pi but also provide the clues about the unknown genes involved in phosphorus homeostasis.
Project description:Total mRNA was extracted from the root tips (10 mm from the root apex) of wild-type plants (Col-0 accession) and stop1 mutants grown 5 days after germination under optimum conditions and then transferred for 16 hours to low phosphate(Pi), low pH, Al and Fe excess mediums.
Project description:The mitochondrial membrane potential directly powers many critical functions of mitochondria, including ATP production, mitochondrial protein import, and metabolite transport. Its loss is a cardinal feature of aging and mitochondrial diseases, and cells closely monitor membrane potential as an indicator of mitochondrial health. Given its central importance, it is logical that cells would modulate mitochondrial membrane potential in response to demand and environmental cues, but there has been little exploration of this question. We report that loss of the Sit4 protein phosphatase in yeast increases mitochondrial membrane potential mostly by inducing the expression of the electron transport chain but also activates the phosphate starvation response. Indeed, a similarly elevated mitochondrial membrane potential is also elicited by either phosphate starvation or by abrogation of the Pho85-dependent phosphate sensing pathway. This enhanced membrane potential is primarily driven by an unexpected activity of the ADP/ATP carrier. We also demonstrate that this connection between phosphate limitation and enhancement of the mitochondrial membrane potential is evolutionarily conserved as it also is observed in primary and immortalized mammalian cells as well as in Drosophila. These data suggest that the mitochondrial membrane potential is subject to environmental stimuli and intracellular signaling regulation and raise the possibility for therapeutic enhancement even under conditions of mitochondrial dysfunction.
Project description:A fermentation strategies with phosphate feeding was applied to elongate transition inti phosphate limitation for an tryptophan overproducing E. coli strain High frequency sampling together with the applied fermentation strategy should provide high resolution insights into regulatory regimes involved in phosphate response The first sampling timepoint was set as a reference time point after 2,5 h fermentation time to cover phosphate excess conditions. Additional 9 sampling time points were selected based on process dynamics as soon as the phosphate concentrations became sensitive