Project description:Diel cycle is of enormous biological importance in that it imposes temporal structure on ecosystem productivity. In the world oceans, microorganisms form complex communities that carry out about half of photosynthesis and the bulk of life-sustaining nutrient cycling. Within these natural microbial assemblages, photoautotrophs, such as Cyanobacteria, display diel rhythmicity in gene expression. To what extent autotrophs and heterotrophs are impacted by light and dark oscillations and how this collectively influences community structure and functionality remains poorly documented. In this study, we compared eight day/night metaproteome profiles of Cyanobacteria and both free-living and attached bacterial fractions from picoplanktonic communities sampled over two consecutive days from the surface north-west Mediterranean Sea. Our results showed similar taxonomic structure in both free-living and particle-attached bacteria, dominated by Alphaproteobacteria and Gammaproteobacteria. Temporal rhythmicity in protein expression was observed in both Synechococcales and Rhodobacterales in light-dependent processes such as photosynthesis or UV-stress response. Other biological processes, such as phosphorus or amino acid metabolisms, were also found to cycle in phototrophs. In contrast, proteins from the ubiquitous Pelagibacterales remained stable independently of the day/night oscillations. This work integrated for the first time diel comparative metaproteomics on both free-living and particle attached bacterial fractions in coastal oligotrophic environment. Our findings demonstrated a taxa-specific response to diel cycle with a more controlled protein regulation for phototrophs. This study provided additional evidences that timekeeping mechanisms might be widespread among Bacteria, broadening our knowledge on diel microbial assemblage dynamics.
Project description:In plants, programmed cell death (PCD) is involved in both the development and in the response to biotic and abiotic aggressions. In early stages of PCD, mitochondrial membranes are made permeable by the formation of permeability transition pores, whose protein composition is debated. Since flooding stress can produce PCD in several plant species, the first goal of this work was to know if flooding stress could be used to induce PCD in Beta vulgaris roots. To do this, two months old beet plants were flood-stressed from one to five days, and the alterations indicating PCD in stressed beetroot cells were observed with a confocal fluorescence microscope. In addition, cytochrome c was released from mitochondria. After assessing that flood stress induced PCD in beetroots, the composition of mitochondrial protein complexes was observed in control and flood-stressed beetroots. Protein complexes from isolated mitochondria were separated by native gel electrophoresis, and their proteins were identified by mass spectrometry. The spectra count of three isoforms of voltage-dependent anion-selective channels (VDAC) increased after one day of flooding. In addition, the size of the complexes formed by VDAC was higher in beetroots flood-stressed for one day (~200 kDa) compared with non-stressed ones (~100 kDa). Other proteins, like chaperonin CPN60-2, also formed complexes with different masses in control and flood-stressed beetroots. Finally, possible interactions of VDAC with other proteins were found performing a cluster analysis. These results indicate that mitochondrial protein complexes formed by VDAC could be involved in the process of programmed cell death in flood-stressed beetroots
Project description:We comprehensively explored Fas expression (protein and mRNA) and function in lymphocyte activation, apoptosis, proliferation and transcriptome, using flow cytometry, [3H]-thymidine incorporation and microarray analysis in PBMC from HTLV-1 Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP) patients.