Project description:Microbial eukaryote community structure during early phytoplankton blooms in the naturally iron-fertilized Kerguelen area (Southern Ocean) Targeted Locus (Loci)
Project description:Iron and light are typically recognized as major limiting factors controlling phytoplankton growth in the Southern Ocean. Recent field-based evidence suggests, however, that manganese concentrations in this region can be low enough to impact phytoplankton physiology and primary productivity. Our study examined the interactive influence of combined iron and manganese deprivation on protein expression and photophysiology in Phaeocystis antarctica, a key Antarctic phytoplankter, and provide taxon-specific proteomic evidence that natural Southern Ocean Phaeocystis populations regularly experience stress due to combined low manganese and iron availability. In culture, combined low iron and manganese induced large scale changes in the Phaeocystis proteome and resulted in reorganization of key components of the photosynthetic apparatus; these differences were largely distinct from those arising from changes in irradiance. These results implicate manganese availability as an important driver of Southern Ocean productivity and demonstrate the utility of peptide mass spectrometry as a tool for mapping of manganese contributions to HNLC conditions in this region.
Project description:We performed RNA-sequencing experiments to examine the differential regulation of genes in the genome of the Southern Ocean diatom Fragilariopsis cylindrus including diverged alleles. RNA-seq was performed on three replicate samples for each experimental condition. Phytoplankton cells were grown under six different experimental conditions including (1) optimal growth, (2) freezing temperatures, (3) elevated temperature, (4) elevated carbon dioxide concentrations, (5) low iron concentrations and (6) prolonged darkness. Total RNA was extracted using a guanidinium thiocyanate-phenol-chloroform extraction protocol, followed by DNase I treatment and RNA purification (Quiagen). First strand cDNA synthesis was performed using random hexamers. Library preparation was performed using the RNA-seq Sample Prep Kit (Illumina) and sequencing was conducted according to the TruSeq RNA sequencing protocol (Illumina) All samples were sequenced together in one flowcell on one lane.
Project description:Prochlorococcus is a cyanobacterium of abundance in open ocean environments and little is known of its iron requirements or iron metabolism. We used microarrays to measure the whole-genome expression response of Prochlorococcus MED4 and MIT9313 to iron stress and recovery from iron stress.
Project description:Elevated DNA methylation in the first intronic region of the BCL6 locus in B cell lymphomas enforces transcription of the BCL6 gene Promoter tiling arrays were used to investigate the distribution of DNA methylation near the promoter region of BCL6 locus Comparison of DNA methylation at promoter regions of lymphoma (Raji) and myeloma (H929) cell lines by methylated CpG island recovery assay (MIRA-chip)
Project description:Coastal Antarctic marine ecosystems play an important role in carbon cycling due to their highly productive seasonal phytoplankton blooms. Southern Ocean microbes are primarily limited by light and iron (Fe) and can be co-limited by cobalamin (vitamin B12 ). Micronutrient limitation is a key driver of ecosystem dynamics and influences the composition of blooms, which are often dominated by either diatoms or the haptophyte Phaeocystis antarctica, each with varied impacts on carbon cycling. However, the vitamin requirements and ecophysiology of the keystone species P. antarctica remains poorly characterized. Using cultures, physiological analysis, and comparative ’omics we examined the response of P. antarctica to a matrix of Fe-B12 conditions. We show that P. antarctica is not auxotrophic for B12 , as previously suggested, and report new mechanistic insights of its B12 response in cultures of predominantly solitary and colonial cells. Proteomics coupled with proteogenomics detected a B12 -independent methionine synthase fusion protein (MetE-fusion) that is expressed under vitamin limitation and is interreplaced with the B12 -dependent isoform (MetH) in replete conditions. Database searches returned homologs of the MetE-fusion protein in multiple Phaeocystis species and in a wide range of marine microbes, including other photosynthetic eukaryotes with polymorphic life cycles and also bacterioplankton. Furthermore, MetE-fusion homologs were found to be expressed in metaproteomic and metatranscriptomic field samples in polar and more geographically widespread regions. As climate change impacts micronutrient availability in the coastal Southern Ocean, our finding that P. antarctica has a flexible B12 metabolism has implications for its relative fitness compared to B12 -auxotrophic diatoms.
Project description:Four seed composition mutants (known as G15FN-109-1, G15FN-12-1, G15FN-23-3, and G15FN-54-3) were identified in a soybean fast neutron population developed in southern U.S. lines. The parent line for G15FN-109-1 is G00-3880, while the parent line for the other three mutants is G00-3213. Each mutant was compared to its respective parent line using CGH to identify the causative region/gene associated with the seed composition phenotypes.
Project description:The Antarctic krill provides central ecosystems services to the Southern Ocean grazing on autotroph and heterotoph diet and constituting the dominant food source for higher trophic levels. Moreover, E. superba's extensive equipment with biomacromolecule hydrolysing enzymes represents a largely untapped resource for applied purposes. The proteome compendium of krill provides a valuable basis for future studies on krill biology (e.g., metabolism, development, migration behaviour), for krill's contribution to organic matter turnover in the Southern Ocean, as well as for multilevel biotechnological prospecting.