Project description:Four Fe(II) concentrations (0.03, 0.09, 0.12 & 0.75 mM) were tested to investigate the stimulation and inhibition effects of ferrous iron on anammox bacterial activity. RNAs were extracted from the cultures, and the synthesized cDNAs by reverse transcription were used to carry out GeoChip analysis, by which the functional communities and expression level differences in functional genes under different Fe(II) concentrations conditions were obtained, and the response of anammox bacteria to Fe(II) stimulation and inhibition are speculated.
Project description:Iron (Fe) is an important growth limiting factor for diatoms and its availability is further restricted by changes in the carbonate chemistry of the water. We investigated the physiological attributes and transcriptional profiles of the diatom Thalassiosira pseudonana grown on a day:night cycle under different CO2/pH and iron concentrations, that in combination generated available iron (Fe’) concentrations of 1160, 233, 58 and 12 pM. We found the light-dark conditions to be the main driver of transcriptional patterns, followed by Fe’ concentration and CO2 availability, respectively. At the highest Fe’ (1160 pM), 55% of the transcribed genes were differentially expressed between day and night, whereas at the lowest Fe’ (12 pM), only 28% of the transcribed genes displayed comparable patterns. While Fe limitation disrupts the diel transcriptional patterns for genes in most central metabolism pathways, the diel periodicity of light- signaling molecules and glycolytic genes, was relatively robust in response to reduced Fe’. Moreover, we identified a non-canonical splicing of transcripts encoding triose-phosphate isomerase, a key-enzyme of glycolysis, generating transcript isoforms that would encode proteins with and without an active site. Transcripts that encoded an active enzyme maintained a diel pattern at low Fe’, while transcripts that encoded the non-active enzyme lost the diel pattern. This work illustrates the interplay between nutrient limitation and transcriptional regulation over the diel cycle. Considering that future ocean conditions will reduce the availability of Fe in many parts of the oceans, our work identifies some of the regulatory mechanisms that may shape future ecological communities.
Project description:Iron (Fe) is an essential element to plants, but can be harmful if accumulated to toxic concentrations. Fe toxicity can be a major nutritional disorder in rice (Oryza sativa) when cultivated under waterlogged conditions, as a result of excessive Fe solubilization of in the soil. However, little is known about the basis of Fe toxicity and tolerance at both physiological and molecular level. Here we aim at understand the genotypic differences in two rice cultivars with contrasting phenotypes under Fe toxicity.
Project description:Several phytohormones and other small molecules have been demonstrated to be involved in iron (Fe) homeostasis. However, how salicylic acid (SA), an essential hormone in plant immunity and defense responses, participates in Fe-deficiency responses in plants is largely unknown. Here, we took advantage of a SA biosynthesis defect mutant phytoalexin deficient 4 (pad4: T-DNA Salk_089936) to explore the possible effects of endogenous SA on the morphological and physiological responses to Fe deprivation. Under a Fe-deficiency treatment, Col-0 showed more severe leaf chlorosis and root growth inhibition compared with the pad4 mutant. The soluble Fe concentrations were significant higher in pad4 than Col-0 under the Fe-deficiency treatment, suggesting that a mutation in the PAD4 gene may alleviate the Fe-deficiency-induced symptoms by regulating the soluble Fe concentrations. Furthermore, a SA signaling maker line (PR1promoter: GUS) was used to investigate how Fe deficiency affects endogenous SA biosynthesis and metabolism. The data showed that Fe deficiency significantly induced SA accumulation in Col-0, and the loss function of PAD4 blocked this process. The requirement of endogenous SA accumulation for Fe-deficiency responses was confirmed using a series of SA biosynthetic mutants and transgenic lines.
Project description:IRT1 is the root high-affinity Fe uptake system. Despite severe Fe deficiency symptoms and reduced Fe levels in the shoots of irt1 mutants, we find that root Fe concentrations are higher in the irt1-2 mutant than in the wild type, unexpectedly. The goal of this experiment was to identify candidate transcripts contributing to the observed alteration in root-to-shoot Fe partitioning of irt1. We analysed gene expression in shoots and roots of the wild type grown under control conditions, the wild type exposed to severe Fe deficiency for 5 d, as well as of the irt1-2 (pam42) mutant grown under control conditions.