Project description:The diatoms Thalassiosira hyalina and Nitzschia frigida are important members of Arctic pelagic (open-water) and sympagic (ice-associated) microalgal communities. We investigated here the molecular mechanisms these algae apply to cope with abrupt high light exposure (Shift from 20 to 380 µmol photons m-2 s-1, resembling upwelling or ice break-up). Experiments were done under contemporary as well as future pCO2 (400 vs. 1000 µatm) to investigate whether [CO2] or pH modulate the reactions to high light intensities. After proper acclimation to the low-light regime, cells were sampled (= 0 hours), then exposed to the high-light treatment expression patterns were followed over 120h. Transcriptomic data were discussed also in the light of an accompanying physiological dataset from the same experiment (Ane Kvernvik et al. in prep).
Project description:We have studied the transcriptional, metabolic and photo-physiological responses to light of different spectral quality in the marine diatom Phaeodactylum tricornutum through time-series studies of cultures exposed to equal doses of photosynthetically usable radiation of blue, green and red light. The experiments showed that short-term differences in gene expression and profiles are mainly light quality-dependent. Transcription of photosynthesis-associated nuclear genes was activated mainly through a light quality-independent mechanism likely to rely on chloroplast-to-nucleus signaling. In contrast, genes encoding proteins important for photoprotection and PSII repair were highly dependent on a blue light receptor-mediated signal. Changes in energy transfer efficiency by light-harvesting pigments were spectrally dependent; furthermore, a declining trend in photosynthetic efficiency was observed in red light. The combined results suggest that diatoms possess a light quality-dependent ability to activate photoprotection and efficient repair of photodamaged PSII. In spite of approximately equal numbers of PSII-absorbed quanta in blue, green and red light, the spectral quality of light is important for diatom responses to ambient light conditions.
Project description:Limited systems-level understanding of oil synthesis in wild oleaginous algae has hindered the development of microalgal feedstock. Nannochloropsis is a small unicellular microalgae widely distributed in oceans and fresh water. In many large-scale and pilot-scale outdoor cultivation facilities, Nannochloropsis strains have been found to be capable of robust growth when supplied with flue gases, naturally accumulating large quantities of oils in a stationary phase, and exhibiting resistance to environmental contaminants. The rich genomic resources, compact genomes, resistance to foreign DNA invasion, wide ecological adaptation, large collections of natural strains and the demonstrated ability to grow on a large scale suggested Nannochloropsis can serve as research models and platform strains for economical and scalable photosynthetic production of fuels and chemicals. To untangle the intricate genome-wide networks underlying the robust biomass accumulation and oil production in Nannochloropsis, we applied high-throughput mRNA-sequencing and reconstructed the structure and dynamics of the genome-wide functional network underlying robust microalgal triacylglycerol (TAG) production in Nannochloropsis oceanica, by tracking the genome-wide, single-base-resolutiontranscript change for the complete time-courses of nitrogen-depletion-induced TAG synthesis. Nannochloropsis oceanica IMET1 cells were grown in liquid cultures under continuous light (approximately 50 M-BM-5mol photons m-2 s-1) at 25M-bM-^DM-^C and aerated by bubbling with a mixture of 1.5% CO2 in air. Mid-logarithmic phase algal cells were collected and washed three times with axenic seawater. Equal numbers of cells were re-inoculated in nitrogen replete medium (Control condition or C, i.e. N+) and nitrogen deprived medium (N deficiency or N, i.e. N-) with 50M-BM-5mol m-2 s-1 light intensity, respectively. Cell aliquots were collected for RNA isolation after being transferred to the designated conditions for 3h, 4h, 6h, 12h, 24h and 48h. Three biological replicates of algal cultures were established under each of the above M-bM-^@M-^\CM-bM-^@M-^] (i.e. N+) and M-bM-^@M-^\NM-bM-^@M-^] (i.e. N-) conditions, respectively. In total, 36 samples collected at six time points (3h,4h,6h,12h,24h and 48h) were used for mRNA-Seq library preparation and then submitted to Illumina HiSeq 2000 for sequencing.
Project description:How epigenetic deregulation affects gene expression patterns in subclones of the same tumor is poorly known. Peritoneal Carcinomatosis (PC) is a condition in which multiple metastases of the same abdominal tumor develop in the peritoneal cavity and intra-peritoneal organs, thus defining different ecosystems of the same cancer. PITCHER addresses the variations in epigenetically regulated gene expression between different subclones of PC in relation with cell mechanoresponses, providing insights on how cancer epigenetic landscapes evolve under environmental pressures and on strategies used by cancer cells to adapt to the transition from one ecosystem to the other.
PITCHER is a network of 10 teams from Lyon, Grenoble and Marseille, based on data and specimen collection of patients who have undergone a surgery for a peritoneal carcinomatosis of ovarian or colorectal origin. PC lesions and eventually matched specimens of primary tumors will be collected in the same patients at the time of the surgery or eventually retrieved from already existing samples. Epigenetic landscapes will be analyzed by a bioinformatics pipeline combining exome sequencing, transcriptome and methylome to identify "epigenetic hotspots", and their variations across lesions will be evaluated. These analyses will be realized in fresh (when available) or pre-existing samples. When possible, organoid cultures and animal models will be derived from multicellular structures in peritoneal fluids and membrane, cytoskeletal and nucleoskeletal mechanoresponses will be characterized using Atomic Force Microscopy. The role of tumor axonogenesis, a process of neo-formation of axon fibers in tumors, will be addressed. Experimental studies of cell responses to therapy will be performed to derive mathematical predictive models. All components will be integrated in a systems biology map of PC.
Project description:We generated primary cultures from renal cell carcinoma and matched normal primary kidney cortex tubule cell cultures from 3 patients. Early passage cultures of these two cell types were subjected to chromatin accessibility profiling (DNase-seq) and gene expression profiling (RNA-seq). Studying these paired and patient-matched controlled data sets will shed light on the epigenomic changes that underlie transformation of kidney tubules into malignant cancers.
Project description:Because of severe abiotic limitations, Antarctic soils represent simplified ecosystems, where microorganisms are the principle drivers of nutrient cycling. This relative simplicity makes these ecosystems particularly vulnerable to perturbations, like global warming, and the Antarctic Peninsula is among the most rapidly warming regions on the planet. However, the consequences of the ongoing warming of Antarctica on microorganisms and the processes they mediate are unknown. Here, using 16S rRNA gene pyrosequencing and qPCR, we report a number of highly consistent changes in microbial community structure and abundance across very disparate sub-Antarctic and Antarctic environments following three years of experimental field warming (+ 0.5-2°C). Specifically, we found significant increases in the abundance of fungi and bacteria and in the Alphaproteobacteria-to-Acidobacteria ratio. These alterations were linked to a significant increase in soil respiration. Furthermore, the shifts toward generalist or opportunistic bacterial communities following warming weakened the linkage between bacterial diversity and functional diversity. Warming also increased the abundance of some organisms related to the N-cycle, detected as an increase in the relative abundance of nitrogenase genes via GeoChip microarray analyses. Our results demonstrate that soil microorganisms across a range of sub-Antarctic and Antarctic environments can respond consistently and rapidly to increasing temperatures, thereby potentially disrupting soil functioning.