Project description:Here we use a transcriptomic approach to investigate the molecular underpinnings of thermal acclimation in the model diatom species Phaeodactylum tricornutum by comparing the differential gene expression in cultures acclimated to sub-optimal, optimal, and supra-optimal temperatures (10, 20 and 26.5 °C, respectively).
Project description:We have investigated both the response to prolonged darkness and the re-acclimation to “moderate intensity” white irradiance (E = 100 µmol m-2 s-1) in the diatom Phaeodactylum tricornutum, using an integrated approach involving global transcriptional profiling, pigment analyses, imaging and photo-physiological measurements. The responses were studied during continuous white light, after 48 h of dark treatment and after 0.5 h, 6 h, and 24 h of re-exposure to the initial irradiance.
Project description:Diatoms played an essential role in marine primary productivity. Polysaccharide chrysolaminarin and neutral lipid, mainly TAG, were necessary carbon fixation in diatom Phaeodactylum tricornutum. Our study speculated on the metabolism pathway of chrysolaminarin, fatty acid, fatty acid β-oxidation and TAG. Transcriptional levels coordinated with carbon fixation metabolism pathway were conjoint analysis in this study.
Project description:Photosynthetic diatoms are exposed to rapid and unpredictable changes in irradiance and spectral quality, and must be able to adapt their light harvesting systems to varying light conditions. Molecular mechanisms behind light acclimation in diatoms are largely unknown. We set out to investigate the mechanisms of high light acclimation in Phaeodactylum tricornutum using an integrated approach involving global transcriptional profiling, metabolite profiling and variable fluorescence technique. Algae cultures were acclimated to low light (LL), after which the cultures were transferred to high light (HL). Molecular, metabolic and physiological responses were studied at time points 0.5 h, 3 h, 6 h, 12 h, 24 h and 48 h after transfer to HL conditions. The integrated results indicate that the acclimation mechanisms in diatoms can be divided into an initial response phase (0.5 h), an intermediate acclimation phase (3-12 h) and a late acclimation phase (12-48 h). The initial phase is recognized by strong and rapid regulation of genes encoding proteins involved in photosynthesis, pigment metabolism and reactive oxygen species (ROS) scavenging systems. A significant increase in light protecting metabolites occur together with the induction of transcriptional processes involved in protection of cellular structures at this early phase. During the following phases, the metabolite profiling display a pronounced decrease in light harvesting pigments, whereas the variable fluorescence measurements show that the photosynthetic capacity increases strongly during the late acclimation phase. We show that P. tricornutum is capable of swift and efficient execution of photoprotective mechanisms, followed by changes in the composition of the photosynthetic machinery that enable the diatoms to utilize the excess energy available in HL. Central molecular players in light protection and acclimation to high irradiances have been identified. The experiment was designed as a time series, with diatom cultures were harvested at time points 0.5 h, 3 h, 6 h, 12 h, 24 h and 48 h after transfer to high light conditions. The reference samples were kept at low light and harvested in parallel with the treated samples. Three biological replicates were harvested for all samples.
Project description:An experiment was performed to determine the similarities on the RNA level between different conditions where cell division stops in the diatom Phaeodactylum tricornutum. Many of these conditions also increase the accumulation of lipids within the cell or impair photosynthesis. The different metabolic responses were evaluated and the dataset was mined for potential transcriptional regulators of these changes. The experimental setup was as follows: Cells from the pennate diatom Phaeodactylum tricornutum were grown in ESAW medium under continous fluorescent light at 21C in baffled shakeflasks. Exponentially growing cells were harvested by centrifugation and washed twice in 21gr/L NaCL to remove nutrients. Cells were subsequently resuspended in the five different media/conditions (control, darkness, no nitrate, no phosphate, nocodazole).
Project description:Diatoms, which are responsible for up to 40% of the 45 to 50 billion metric tons of organic carbon production each year in the sea, are particularly sensitive to Fe stress. Here we describe the transcriptional response of the pennate diatom Phaeodactylum tricornutum to Fe limitation using a partial genome microarray based on EST and genome sequence data. Processes carried out by components rich in Fe, such as photosynthesis, mitochondrial electron transport and nitrate assimilation are down-regulated to cope with the reduced cellular iron quota. This retrenchment is compensated by nitrogen (N) and carbon (C) reallocation from protein and storage carbohydrate degradation, adaptations to chlorophyll biosynthesis and pigment metabolism, removal of excess electron s by mitochondrial alternative oxidase (AOX), augmented Fe-independent oxidative stress responses, and sensitized iron capture mechanisms. Keywords: Marine phytoplankton, pinnate diatom Wild-type Phaeodactylum tricornutum was grown under Fe replete (10,000 nM) and Fe limiting (5nM) conditions. Partial genome gene expression analysis of iron-inducible genes was conducted using a two-color competitive hybridization microarray.
Project description:Photosynthetic diatoms are exposed to rapid and unpredictable changes in irradiance and spectral quality, and must be able to adapt their light harvesting systems to varying light conditions. Molecular mechanisms behind light acclimation in diatoms are largely unknown. We set out to investigate the mechanisms of high light acclimation in Phaeodactylum tricornutum using an integrated approach involving global transcriptional profiling, metabolite profiling and variable fluorescence technique. Algae cultures were acclimated to low light (LL), after which the cultures were transferred to high light (HL). Molecular, metabolic and physiological responses were studied at time points 0.5 h, 3 h, 6 h, 12 h, 24 h and 48 h after transfer to HL conditions. The integrated results indicate that the acclimation mechanisms in diatoms can be divided into an initial response phase (0.5 h), an intermediate acclimation phase (3-12 h) and a late acclimation phase (12-48 h). The initial phase is recognized by strong and rapid regulation of genes encoding proteins involved in photosynthesis, pigment metabolism and reactive oxygen species (ROS) scavenging systems. A significant increase in light protecting metabolites occur together with the induction of transcriptional processes involved in protection of cellular structures at this early phase. During the following phases, the metabolite profiling display a pronounced decrease in light harvesting pigments, whereas the variable fluorescence measurements show that the photosynthetic capacity increases strongly during the late acclimation phase. We show that P. tricornutum is capable of swift and efficient execution of photoprotective mechanisms, followed by changes in the composition of the photosynthetic machinery that enable the diatoms to utilize the excess energy available in HL. Central molecular players in light protection and acclimation to high irradiances have been identified.