Project description:Dunaliella salina Bardawil (also known as Dunaliella bardawil) is an extremophilic, unicellular green alga from the Chlorophyte lineage. D. salina is found in hypersaline environments where it can tolerate extremes of heat, light, pH, and up to saturating concentrations of salt. The D. salina Bardawil isolate (UTEX LB 2538) was found in a salt pond near the Bardawil Lagoon on the Sinai peninsula in 1976. This isolate of D. salina is the richest natural source of beta-carotene, a highly valuable commercial product. This accession includes an RNA-Seq analysis of D. salina Bardawil cultures grown in iron-replete (1.5 µM) or iron-deficient (0 µM) media.
Project description:The unicellular green alga Dunaliella salina is an attractive model organism for studying photoacclimation responses. Changes in irradiance levels during cell growth affect the organization and structure of the photosystem and the pigments composition. We sequenced the RNA of D. salina to investigate the transcriptomic response of the organism after transitioning from normal light conditions to higher light intensity. Specific transcripts encoding for enzymes involved in photosynthesis were down-regulated, whereas genes involved in the metabolism of carotenoid and triacylglycerol were up-regulated. Genes encoding for photoprotective enzymes related to reactive oxygen species (ROS) scavenging and to the xanthophyll cycle were also up-regulated at higher irradiance levels. The present transcriptomic study would assist in the comprehensive understanding of photoacclimation mechanisms of D. salina.
Project description:Like many microalgae unicellular green alga, Chlamydomonas reinhardtii also accumulates energy rich storage lipid and starch under nutrient-limited conditions, such as phosphorus (P) and nitrogen (N) limitation. To dissect the transcriptional regulation of lipid and starch biosynthesis in response to nutrient limitation, we have characterized the biological role of a candidate regulator: the MYB family transcription factor, PSR1 (phosphorus starvation response 1). Genetically modified (psr1 compromised) and wild-type lines were grown under P limiting and sufficient conditions and assayed at two time points by SOLiD RNA-seq.
Project description:Dunaliella salina, a unicellular and eukaryotic alga, has been found as one of the most salt-tolerant eukaryote with a short growth period and wide practical applications. To elucidate the underlying molecular mechanism involved in the response to salinity and its different effects, RNA-seq was used for global transcriptome profiling of D. salina exposed to NaCl, Sorbiol and H2O2 stress. To maintain osmotic pressure homeostasis under suboptimal environment condition, starch breakdown catalyzed by both alpha-amylase (AMY) and glycogen phosphorylase (PYG) with consecutive expression patterns and low activity of PYG at the beginning of salt stress might be caused by a shortage of ATP because of impaired photosynthesis. Moreover, clustering analysis of differentially expressed genes (DEGs) indicated that starch and sucrose metabolism as well as glycerol metabolism reprogrammed under high salt stress only. For redox homeostasis, glycerol-3-phosphate shuttle performed by mitochondrial glycerol-3-phosphate dehydrogenases (GPDHs) participates the redox imbalance under abiotic stresses. c23777_g1 is a gene of D. salina involved in glycerol 3 phosphate (G3P) shuttle under various abiotic stresses while c25199_g1 is a gene of G3P shuttle induced only by osmotic stress.
Project description:Dunaliella tertiolecta is an extremophilic, green alga from the Chlorophyte lineage. It is found in coastal marine environments around the world. D. tertiolecta can tolerate extremes of heat, light, pH, and salinity. D. tertiolecta is under development for the production biofuels and other bioproducts because it can produce large quantities of neutral lipids, and it can be grown in open raceway ponds using only the inputs of seawater and sunlight. This isolate of D. tertiolecta (UTEX LB 999) was found in Oslofjord, Norway in 1938. This accession includes an RNA-Seq analysis of D. tertiolecta cultures grown in iron-replete (1.5 µM) or iron-deficient (0 µM) media.
Project description:The unicellular microalga Dunaliella salina is one of the halotolerant and cell wall-less green microalgae in Dunaliella genus. The ability of halotolerance in Dunaliella is attributed to the accumulation of glycerol. Both sugar made by photosynthesis and starch serve as carbon sources for glycerol biosynthesis. Quantitative PCR-based analyses concluded no apparent transcriptional regulation of glycerol, carbon fixation, and starch metabolisms upon salinity stresses. To examine whether or not transcriptional regulation is involved at the transcriptomic level, we assembled a de novo deep sequencing transcriptome. By using a pathway-based approach, we show that low- and high-salt (i.e., 0.5M versus 2M NaCl) adapted cells share a common transcriptomic profile and that subsets of ESTs associated with energy metabolisms are less affected upon salinity stress. We find that enzymes involved in glycerol, carbon fixation, and starch metabolisms are encoded by multiple EST isoforms. We show that EST isoforms encoding dihydroacetone reductase in glycerol metabolism, phosphoglycerate kinase in carbon fixation, and beta-amylase and fructobiphosphate aldolase in starch metabolism display a correlated transcriptional level change to the alteration of glycerol and starch contents upon salinity stresses. Taken together, our results demonstrate that some enzymes involved in glycerol, carbon fixation, and starch metabolisms are regulated at the transcriptional level upon salinity stresses. Furthermore, our analyses indicate that energy metabolisms are not drastically affected upon salinity stresses, consistent with its ability to adapt to a wide range of salinities.