Proteomic profile in the mussel Perna viridis after short-term exposure to the brown tide alga Aureococcus anophagefferens.

Blooms of Aureococcus anophagefferens, referred to as brown tides are responsible for massive mortalities and recruitment failure of some bivalves. However, the molecular mechanisms underlying the toxicity remain elusive despite its biological significance, and the information currently available on the molecular effects is still insufficient. In this study, to evaluate the toxicity and associated mechanism of A. anophagefferens on bivalves, we analyzed the protein expression profiles in digestive glands of the A. anophagefferens-exposed Perna viridis by using iTRAQ. A total of 3138 proteins were identified in the digestive glands of A. anophagefferens-exposed P. viridis based on iTRAQ. Amongst, a repertoire of 236 proteins involved in cell, cell part, catalytic activity, metabolic process, biological regulation, immune system process, and response to stimulus were found to be differentially expressed. Functional analysis of the differentially expressed proteins demonstrated that innate immune system of P. viridis was activated, and some proteins associated with stress response and lipid metabolism were induced after exposure to A. anophagefferens. Additionally, MDA content, SOD activity and GSH-Px activity was increased significantly in the digestive gland of A. anophagefferens-exposed P. viridis. Taken together, our results indicated that the A. anophagefferens could induce oxidative stress, activate complement system and alter fat acid metabolism of P. viridis.

High light stress triggers distinct proteomic responses in the marine diatom Thalassiosira pseudonana.

BACKGROUND: Diatoms are able to acclimate to frequent and large light fluctuations in the surface ocean waters. However, the molecular mechanisms underlying these acclimation responses of diaotms remain elusive. RESULTS: In this study, we investigated the mechanism of high light protection in marine diatom Thalassiosira pseudonana using comparative proteomics in combination with biochemical analyses. Cells treated under high light (800 µmol photons m-2s-1) for 10 h were subjected to proteomic analysis. We observed that 143 proteins were differentially expressed under high light treatment. Light-harvesting complex proteins, ROS scavenging systems, photorespiration, lipid metabolism and some specific proteins might be involved in light protection and acclimation of diatoms. Non-photochemical quenching (NPQ) and relative electron transport rate could respond rapidly to varying light intensities. High-light treatment also resulted in increased diadinoxanthin + diatoxanthin content, decreased Fv/Fm, increased triacylglycerol and altered fatty acid composition. Under HL stress, levels of C14:0 and C16:0 increased while C20:5ω3 decreased. CONCLUSIONS: We demonstrate that T. pseudonana has efficient photoprotective mechanisms to deal with HL stress. De novo synthesis of Ddx/Dtx and lipid accumulation contribute to utilization of the excess energy. Our data will provide new clues for in-depth study of photoprotective mechanisms in diatoms.

Understanding strategy of nitrate and urea assimilation in a Chinese strain of Aureococcus anophagefferens through RNA-seq analysis.

Aureococcus anophagefferens is a harmful alga that dominates plankton communities during brown tides in North America, Africa, and Asia. Here, RNA-seq technology was used to profile the transcriptome of a Chinese strain of A. anophagefferens that was grown on urea, nitrate, and a mixture of urea and nitrate, and that was under N-replete, limited and recovery conditions to understand the molecular mechanisms that underlie nitrate and urea utilization. The number of differentially expressed genes between urea-grown and mixture N-grown cells were much less than those between urea-grown and nitrate-grown cells. Compared with nitrate-grown cells, mixture N-grown cells contained much lower levels of transcripts encoding proteins that are involved in nitrate transport and assimilation. Together with profiles of nutrient changes in media, these results suggest that A. anophagefferens primarily feeds on urea instead of nitrate when urea and nitrate co-exist. Furthermore, we noted that transcripts upregulated by nitrate and N-limitation included those encoding proteins involved in amino acid and nucleotide transport, degradation of amides and cyanates, and nitrate assimilation pathway. The data suggest that A. anophagefferens possesses an ability to utilize a variety of dissolved organic nitrogen. Moreover, transcripts for synthesis of proteins, glutamate-derived amino acids, spermines and sterols were upregulated by urea. Transcripts encoding key enzymes that are involved in the ornithine-urea and TCA cycles were differentially regulated by urea and nitrogen concentration, which suggests that the OUC may be linked to the TCA cycle and involved in reallocation of intracellular carbon and nitrogen. These genes regulated by urea may be crucial for the rapid proliferation of A. anophagefferens when urea is provided as the N source.

Molecular and cellular mechanisms of neutral lipid accumulation in diatom following nitrogen deprivation.

BACKGROUND: Nitrogen limitation can induce neutral lipid accumulation in microalgae, as well as inhibiting their growth. Therefore, to obtain cultures with both high biomass and high lipid contents, and explore the lipid accumulation mechanisms, we implemented nitrogen deprivation in a model diatom Phaeodactylum tricornutum at late exponential phase. RESULTS: Neutral lipid contents per cell subsequently increased 2.4-fold, both the number and total volume of oil bodies increased markedly, and cell density rose slightly. Transcriptional profile analyzed by RNA-Seq showed that expression levels of 1213 genes (including key carbon fixation, TCA cycle, glycerolipid metabolism and nitrogen assimilation genes) increased, with a false discovery rate cut-off of 0.001, under N deprivation. However, most light harvesting complex genes were down-regulated, extensive degradation of chloroplast membranes was observed under an electron microscope, and photosynthetic efficiency declined. Further identification of lipid classes showed that levels of MGDG and DGDG, the main lipid components of chloroplast membranes, dramatically decreased and triacylglycerol (TAG) levels significantly rose, indicating that intracellular membrane remodeling substantially contributed to the neutral lipid accumulation. CONCLUSIONS: Our findings shed light on the molecular mechanisms of neutral lipid accumulation and the key genes involved in lipid metabolism in diatoms. They also provide indications of possible strategies for improving microalgal biodiesel production.

Rho-associated coiled kinase inhibitor Y-27632 promotes neuronal-like differentiation of adult human adipose tissue-derived stem cells.

BACKGROUND: Y-27632 is a specific inhibitor of Rho-associated coiled kinase (ROCK) and has been shown to promote the survival and induce the differentiation of a variety of cells types. However, the effects of Y-27632 on adult human adipose tissue-derived stem cells (ADSCs) are unclear. This study aimed to investigate the effects of Y-27632 on the neuronal-like differentiation of ADSCs. METHODS: ADSCs were isolated from women undergoing plastic surgery and cultured. ADSCs were treated with different doses of Y-27632 and observed morphological changes under microscope. The expression of nestin, neuron specific enolase (NSE) and microtubule-associated protein-2 (MAP-2) in ADSCs treated with Y-27632 was detected by immunocytochemistry and Western blotting analysis. RESULTS: Y-27632 had the potency to induce neuronal-like differentiation in ADSCs in a dose-dependent manner. Moreover, the differentiation induced by Y-27632 was recovered upon drug withdraw. ADSCs treated with Y-27632 expressed neuronal markers such as NSE, MAP-2 and nestin while untreated ADSCs did not express these markers. CONCLUSION: Selective ROCK inhibitor Y-27632 could potentiate the neuronal-like differentiation of ADSCs, suggesting that Y-27632 could be utilized to induce the differentiation of ADSCs to neurons and facilitate the clinical application of ADSCs in tissue engineering.

Multivariate statistical and GIS-based approach to identify source of anthropogenic impacts on metallic elements in sediments from the mid Guangdong coasts, China.

Growing concerns surround the mid Guangdong coasts, one of China's fastest and developing economical regions. To study the environmental impacts of economic and industrial development, we measured ten metallic elements (Hg, Pb, Cu, Zn, Fe, Al, Ni, Sr, Li, and Co) in surface sediments from nineteen stations in three bays. All these metals showed concentrations substantially higher than their background values, suggesting possible anthropogenic pollution. Highest metal levels were close to the nuclear power plants likely as a result of nuclear waste discharges. Results revealed that Hg, Pb, and Sr largely originated from human activities, while Cu, Ni, Co, Al, and Fe mainly from natural rock weathering. Two types of anthropogenic sources were identified through a principal component analysis, one from shipping industry, port transport service and nuclear power plants, and the other from municipal sewage and coal power plant.

Molecular ecological responses of dinoflagellate, Karenia mikimotoi to environmental nitrate stress.

Karenia mikimotoi is one of the most important harmful algal species in the Chinese coastal waters, and which produce hemolytic toxins and ichthyotoxins, resulting in devastating economic losses. Previous studies demonstrated that the increase of nitrate concentration could promote the growth and reproduction of K. mikimotoi. However, the intrinsic mechanisms regarding the effects of nitrate on the K. mikimotoi photosynthesis, nucleic acid replication and differential protein expression remain to be elucidated. Our study demonstrated that nitrate stress inhibited growth of K. mikimotoi (p<0.01). Algal chlorophyll fluorescence intensity varied slightly while algal cell cycle succession was significantly retarded by nitrate stress (p<0.05). Sixteen proteins were detected only in nitrate-limited cultures which related to nitrate transport, signal transduction, amino acid metabolism, DNA repair and hemolysin manufacture. Eleven proteins were detected only in nitrate-replete sample and were related to photorespiration, reproduction and growth, assistance of protein modification, cytoskeleton stability and signal transduction. Based on analysis of differential proteomic functional annotations, we hypothesized a proteomic response mechanism of K. mikimotoi to environmental nitrate stress.

[Population dynamics of Alexandrium tamarense and its relations with environmental factors in Nanji Islands sea area of Zhejiang Province].

Based on the investigation in Nanji Islands sea area of Zhejiang Province from April 2006 to March 2007, the dynamics of Alexandrium tamarense and its relations with environmental factors were studied. In the study sea area, A. tamarense cells could only be found in spring (from April to June), and the cell abundance was of single peak curve, with the highest (12250 cells x L(-1)) in surface water on 8th of May. Higher cell abundance of A. tamarense was found at the water temperature of 18.5 degrees C - 19.5 degrees C, salinity of 29.5 per thousand - 31.0 per thousand, and lower PO4-P concentration, but no correlation was observed between A. tamarense cell abundance and water dissolved inorganic N concentration. Linear stepwise regression revealed that there was a significant positive correlation between the cell abundance of A. tamarense and the ratio of water dissolved inorganic N to PO4-P.

[Sodium dichlorinated isocyanuric acid and trichloroisocyanuric acid for removing cells of Phaeochystis globosa].

Removal and control of Phaeochystis globosa cells by sodium dichlorinated isocyanuric acid and tri-chloroisocyanuric acid were studied. Removal efficiency of the two algaecides was contrasted and removal mechanism was also discussed. The results suggest both of the algaecides have excellent ability to remove and control Phaeochystis globosa cells. Hypochlorous acid is released slowly by the two algaecides and maintains it's stabilization. The effective concentration of available chlorine is 4.5 mg/L. The removal efficiency is more than 90% within 24 hours at the available chlorine's dosage of 5.0 mg/L. Trichloroisocyanuric acid could remove Phaeochystis globosa cells more effectively than sodium dichlorinated isocyanuric acid when concentration of available chlorine was more than 5.0 mg/L. The conclusion was identified by t test of available chlorine and removal efficiency.