Dissolved organic phosphorus promotes Cyclotella growth and adaptability in eutrophic tropical estuaries.

Dissolved organic phosphorus (DOP) is an important nutrient for phytoplankton growth in oligotrophic oceans. However, little is known about the impact of DOP on phytoplankton growth in eutrophic waters. In the present study, we conducted field monitoring as well as in situ and laboratory experiments in the Pearl River estuary (PRE). Field observations showed an increase in the nitrogen-to-phosphorus ratio and DOP in recent years in the PRE. The phytoplankton community was dominated by nanophytoplankton Cyclotella in the upper and middle estuary, with high concentrations of DOP and light limitation during the ebb stage of the spring to neap tide in summer. The relative abundance of Cyclotella in natural waters was higher after enrichment with estuarine water with a background of 0.40-0.46 µM DOP, even when dissolved inorganic phosphorus was sufficient (0.55-0.76 µM). In addition, the relative abundance of Cyclotella in natural waters was higher after enrichment with phosphoesters. Laboratory culture results also confirmed that phosphoesters can enhance the growth rate of Cyclotella cryptica. Our study highlights that Cyclotella can become the dominant species in estuaries with increased levels of phosphoesters and low and fluctuating light adaptability and under the joint effect of dynamic processes such as upwelling and tides. Our results provide new insights into the role of Cyclotella in biogeochemical cycles affected by DOP utilization and potential applications in relieving the hypoxia of tropical eutrophic estuaries.IMPORTANCEThis study provides evidence that Cyclotella can become the dominant species in estuaries with increased levels of phosphoesters and low and fluctuating light adaptability and under the joint effect of dynamic processes such as upwelling and tides. Our study provides new insights into the role of Cyclotella in biogeochemical cycles affected by dissolved organic phosphorus utilization, especially affected by anthropogenic inputs and climate change. Potential applications include relieving the hypoxia of tropical eutrophic estuaries.

Cyano-Functionalized Pyrazine: A Structurally Simple and Easily Accessible Electron-Deficient Building Block for n-Type Organic Thermoelectric Polymers.

Developing low-cost and high-performance n-type polymer semiconductors is essential to accelerate the application of organic thermoelectrics (OTEs). To achieve this objective, it is critical to design strong electron-deficient building blocks with simple structure and easy synthesis, which are essential for the development of n-type polymer semiconductors. Herein, we synthesized two cyano-functionalized highly electron-deficient building blocks, namely 3,6-dibromopyrazine-2-carbonitrile (CNPz) and 3,6-Dibromopyrazine-2,5-dicarbonitrile (DCNPz), which feature simple structures and facile synthesis. CNPz and DCNPz can be obtained via only one-step reaction and three-step reactions from cheap raw materials, respectively. Based on CNPz and DCNPz, two acceptor-acceptor (A-A) polymers, P(DPP-CNPz) and P(DPP-DCNPz) are successfully developed, featuring deep-positioned lowest unoccupied molecular orbital (LUMO) energy levels, which are beneficial to n-type organic thin-film transistors (OTFTs) and OTEs performance. An optimal unipolar electron mobility of 0.85 and 1.85 cm2 V-1 s-1 is obtained for P(DPP-CNPz) and P(DPP-DCNPz), respectively. When doped with N-DMBI, P(DPP-CNPz) and P(DPP-DCNPz) show high n-type electrical conductivities/power factors of 25.3 S cm-1 /41.4 µW m-1 K-2 , and 33.9 S cm-1 /30.4 µW m-1 K-2 , respectively. Hence, the cyano-functionalized pyrazine CNPz and DCNPz represent a new class of structurally simple, low-cost and readily accessible electron-deficient building block for constructing n-type polymer semiconductors.

Microbial Communities Are Shaped by Different Ecological Processes in Subtropical Reservoirs of Different Trophic States.

Understanding microbial community structure and the underlying control mechanisms are fundamental purposes of aquatic ecology. However, little is known about the seasonality and how trophic conditions regulate plankton community in subtropical reservoirs. In this study, we study the prokaryotic and picoeukaryotic communities and their interactions during wet and dry seasons in two subtropical reservoirs: one at oligotrophic state and another at mesotrophic state. Distinct microbial community compositions (prokaryotes and picoeukaryotes) and seasonal variation pattern were detected in the oligotrophic and mesotrophic reservoirs. The interactions between prokaryotic and picoeukaryotic communities were more prevalent in the oligotrophic reservoir, suggesting enhanced top-down control of small eukaryotic grazers on the prokaryotic communities. On the other hand, the microbial community in the mesotrophic reservoir was more influenced by physico-chemical parameters and showed a stronger seasonal variation, which may be the result of distinct nutrient levels in wet and dry seasons, indicating the importance of bottom-up control. Our study contributes to new understandings of the environmental and biological processes that shape the structure and dynamics of the planktonic microbial communities in reservoirs of different trophic states.

Community Dynamics of Free-Living and Particle-Attached Bacteria over Sequential Blooms of Heterotrophic Dinoflagellate Noctiluca scintillans and Mixotrophic Ciliate Mesodinium rubrum.

During a series of blooms of Noctiluca scintillans and Mesodinium rubrum, we applied high-throughput sequencing of the 16S rRNA gene to investigate the population dynamics of free-living (FL) and particle-attached (PA) bacteria in an attempt to evaluate the influence of protozoan bloom-induced disturbances on the structuring of these two communities. Our findings revealed that the FL and PA bacterial community compositions (BCCs) displayed distinct profiles during sequential blooms, and the PA flora responded more dynamically to these pulse perturbations. The dominant bacterial groups (e.g., Flavobacteriaceae, Rhodobacteraceae, Vibrionaceae, and SAR11 subclade I) in these two communities displayed different levels of connectivity with the bloom-causative species and environmental factors. In addition, more FL bacterial groups were associated with M. rubrum, while more PA bacterial groups were related to N. scintillans. Potential endocytic bacteria of N. scintillans, particularly Vibrionaceae and Rickettsiaceae, opportunistically thrived at the peak of the bloom, suggesting that they could be important players influencing the dynamics and biogeochemical cycling of the blooms. Overall, disparities in the substrate preferences and thermal niches of various bacterial taxa as well as the short duration of the blooms (1 to 3 days) contributed to the diverse responses of the FL and PA bacterial communities to these protozoan blooms. Our research provides insight into the responses of FL and PA bacterial communities to blooms caused by protozoa like N. scintillans and M. rubrum and highlights the ecological significance of certain keystone bacterial groups during this kind of cosmopolitan protozoan bloom. IMPORTANCE Shifts in the bacterioplankton community composition during phytoplankton blooms have been studied extensively; however, investigations on protozoan blooms are rare. This study first evaluated the impact of perturbations caused by sequential protozoan blooms of the heterotrophic dinoflagellate Noctiluca scintillans and the mixotrophic ciliate Mesodinium rubrum on the structuring of these two bacterial communities. Our findings shed light on the responses of these two bacterial communities to such cosmopolitan protozoan blooms and highlight the possible ecological significance of certain keystone bacterial groups during these blooms. This research prepares the way for more focused studies that will help in understanding the roles that bacteria play during protozoan blooms and their impact on environmental health.

Multi-Omics Profiling Reveals Resource Allocation and Acclimation Strategies to Temperature Changes in a Marine Dinoflagellate.

Temperature is a critical environmental factor that affects the cell growth of dinoflagellates and bloom formation. To date, the molecular mechanisms underlying the physiological responses to temperature variations are poorly understood. Here, we applied quantitative proteomic and untargeted metabolomic approaches to investigate protein and metabolite expression profiles of a bloom-forming dinoflagellate Prorocentrum shikokuense at different temperatures. Of the four temperatures (19, 22, 25, and 28°C) investigated, P. shikokuense at 25°C exhibited the maximal cell growth rate and maximum quantum efficiency of photosystem II (Fv/Fm) value. The levels of particulate organic carbon (POC) and nitrogen (PON) decreased with increasing temperature, while the POC/PON ratio increased and peaked at 25°C. Proteomic analysis showed proteins related to photoreaction, light harvesting, and protein homeostasis were highly expressed at 28°C when cells were under moderate heat stress. Metabolomic analysis further confirmed reallocated amino acids and soluble sugars at this temperature. Both omic analyses showed glutathione metabolism that scavenges the excess reactive oxygen species, and transcription and lipid biosynthesis that compensate for the low translation efficiency and plasma membrane fluidity were largely upregulated at suboptimal temperature. Higher accumulations of glutathione, glutarate semialdehyde, and 5-KETE at 19°C implied their important roles in low-temperature acclimation. The strikingly active nitrate reduction and nitrogen flux into asparagine, glutamine, and aspartic acid at 19°C indicated these three amino acids may serve as nitrogen storage pools and help cells cope with low temperature. Our study provides insights into the effects of temperature on dinoflagellate resource allocation and advances our knowledge of dinoflagellate bloom formation in marine environments. IMPORTANCE Marine phytoplankton is one of the most important nodes in global biogeochemical cycle. Deciphering temperature-associated marine phytoplankton cell stoichiometric changes and the underlying molecular mechanisms are therefore of great ecological concerns. However, knowledge of how phytoplankton adjust the cell stoichiometry to sustain growth under temperature changes is still lacking. This study investigates the variations of protein and metabolite profiles in a marine dinoflagellate across temperatures at which the field blooms usually occur and highlights the temperature-dependent molecular traits and key metabolites that may be associated with rapid cell growth and temperature stress acclimation.

Management of Fused Anterior Teeth: Review and Clinical Report.

The phenomenon of fusion is a type of tooth dysplasia, but few studies have systematically described the treatment of this kind of abnormality. This paper summarizes the treatment methods for fused teeth and classifies the management schemes according to whether the pulp is fused. Then, the treatment for a patient with bilateral anterior tooth fusion is reported. After orthodontic treatment, porcelain veneers were used to restore the normal shape and aesthetic appearance of the anterior teeth.

Gamma4: a genetically versatile Gammaproteobacterial nifH phylotype that is widely distributed in the North Pacific Ocean.

Despite the increasing reports of non-cyanobacterial diazotrophs (NCDs) in pelagic waters, only one NCD (GammaA) has been relatively well described, whose genome and physiology are still unclear. Here we present a comprehensive analysis of the biogeography and ecophysiology of a widely distributed NCD, Gamma4. Gamma4 was the most abundant Gammaproteobacterial NCD along transects across the subtropical North Pacific. Using quantitative PCR, Gamma4 was detectable throughout the surface waters of North Pacific (7°N-55°N, 138°E-80°W), whereas GammaA was detected at <2/3 of the stations. Gamma4 was abundant during autumn-winter and positively correlated with chlorophyll a, while GammaA thrived during spring-summer and was positively correlated with temperature. Environmental clones affiliated with Gamma4 were widely detected in pelagic waters, oxygen minimum zones and even dinoflagellate microbiomes. By analysing the metabolic potential of a genome of Gamma4 reconstructed from the Tara Oceans dataset, we suggest that Gamma4 is a versatile heterotrophic NCD equipped with multiple strategies in scavenging phosphate (and iron) and for respiratory protection of nitrogenase. The transcription of nitrogenase genes is putatively regulated by Fnr-NifL-NifA and GlnD-GlnK systems that respond to intracellular oxygen and glutamate concentration. These results provide important implications for the potential life strategies of pelagic NCDs.

Distinct interaction effects of warming and anthropogenic input on diatoms and dinoflagellates in an urbanized estuarine ecosystem.

Diatoms and dinoflagellates are two major bloom-forming phytoplankton groups in coastal ecosystems and their dominances will notably affect the marine ecosystems. By analyzing an 18-year monthly monitoring dataset (2000-2017) in the Pearl River Estuary (one of the most highly urbanized and populated estuarine in the world), we observe an increasing trend of the diatom to dinoflagellate ratio (Diatom/Dino). As revealed by multiple statistical models (generalized additive mixed model, random forest, and gradient boosting algorithms), both groups are positively correlated with temperature. Diatoms are positively correlated with nitrate and negatively correlated with ammonium while dinoflagellates show an opposite pattern. The Diatom/Dino trend is explained by an altered nutrient composition caused by a decadal increase in anthropogenic input, at which nitrate increased rapidly while ammonium and phosphate were relatively constant. Regarding the interaction of warming and nutrient dynamics, we observe an additive effect of warming and nitrate enrichment that promotes the increase in diatom cell density, while the dinoflagellate cell density only increases with warming when nutrients are depleted. Our models predict that the Diatom/Dino ratio will further increase with increasing anthropogenic input and global warming in subtropical estuarine ecosystems with nitrate as the dominant inorganic nitrogen; its ecological consequences are worthy of further investigation.

Bacterioplankton Metacommunity Processes across Thermal Gradients: Weaker Species Sorting but Stronger Niche Segregation in Summer than in Winter in a Subtropical Bay.

Thermal effluents from nuclear power plants greatly change the environmental and ecological conditions of the receiving marine water body, but knowledge about their impact on microbial ecology is limited. Here we used high-throughput sequencing of the 16S rRNA gene to examine marine bacterioplankton metacommunity assembly across thermal gradients in two representative seasons (i.e., winter and summer) in a subtropical bay located on the northern coast of the South China Sea. We found high heterogeneity in bacterioplankton community compositions (BCCs) across thermal gradients and between seasons. The spatially structured temperature gradient created by thermal effluents was the key determinant of BCCs, but its influence differed by season. Using a metacommunity approach, we found that in the thermal discharge area, i.e., where water is frequently exchanged with surrounding seawater and thermal effluent water, the BCC spatial patterns were shaped by species sorting rather than by mass effects from surrounding seawater or by dilution of thermal effluent water by surrounding seawater. However, this effect of species sorting was weaker in summer than in winter seawater. In both seasons, the bacterioplankton community structure was predominately determined by niche sharing; however, the relative importance of niche segregation was enhanced in summer seawater. Our findings suggest that for the seasonal differences in metacommunity processes, the BCCs of subtropical summer seawater were more sensitive to temperature and were more difficult to predict than those of winter seawater in the face of different intensities of thermal impacts.IMPORTANCE Understanding the mechanisms of bacterial community assembly across environmental gradients is one of the major goals of marine microbial ecology. Thermal effluents from two nuclear power plants have been present in the subtropical Daya Bay for more than 20 years and have generated a comparatively stable and long thermal gradient (a temperature increase from 0 to 10°C). The environmental patches across thermal gradients are heterogeneous and very strongly interconnected on a microbial scale; thus, this is a useful model for the study of the metacommunity processes (i.e., patch dynamics, species sorting, mass effects, and neutral processes) that underlie marine bacterioplankton assembly. The significance of our research is to reveal how environmental conditions and dispersal-related processes interact to influence bacterioplankton metacommunity processes and their seasonal differences across thermal gradients. Our results may advance the understanding of marine microbial ecology under future conditions of global warming.

Polychlorinated Biphenyl Quinone Promotes Macrophage-Derived Foam Cell Formation.

Polychlorinated biphenyls (PCBs) are organic environmental pollutants that are accused of various toxic effects. PCB exposure is widely believed to be associated with atherosclerosis, but the underlying mechanisms are unclear. Although PCBs are easily metabolized, there is rarely information on the effects of their metabolites on atherosclerosis. Currently, we evaluate the effect of 2,3,5-trichloro-6-phenyl-[1,4]-benzoquinone (PCB29-pQ) on the critical phase of atherosclerosis development, that is, the formation of macrophage-derived foam cells. We exposed Ox-LDL-induced RAW264.7 cells to 2.5 µM and 5 µM PCB29-pQ. Varieties of evidence have demonstrated that PCB29-pQ promotes foam cell formation and develops proinflammatory cascade and cell necroptosis. In detail, we observed that PCB29-pQ increased levels of total cholesterol (TC), free cholesterol (FC), triglyceride (TG), and cholesteryl ester (CE) by increasing the cholesterol influx and reducing the cholesterol efflux. Moreover, we found that PCB29-pQ induced inflammatory cytokines, such as tumor necrosis factor (TNF-α), interleukin 6 (IL-6), and IL-1ß, released by activating the mitogen-activated protein kinase (MAPK)-nuclear factor kappa B (NF-κB) inflammatory pathway. In addition, we demonstrated that PCB29-pQ induced cell necroptosis via receptor interacting protein kinases 1 and 3 (RIPK1/3) and a mixed-lineage kinase domain-like (MLKL) pathway. Finally, the overproduction of reactive oxygen species (ROS) by PCB29-pQ played significant roles in these processes, which could be reversed with an antioxidant. Overall, our results indicated that PCB29-pQ promoted the macrophage formation of foam cells, inflammation, and cell necroptosis.

Polychlorinated Biphenyl Quinone Induces Caspase 1-Mediated Pyroptosis through Induction of Pro-inflammatory HMGB1-TLR4-NLRP3-GSDMD Signal Axis.

Polychlorinated biphenyls (PCBs) are one of the most refractory environmental pollutants. Because of their ubiquitous existence in the biological systems (including human body), it is important to investigate their toxic behavior. Our previous findings demonstrated that a high reactive metabolite of PCB, namely PCB29-pQ, causes several programmed cell death (PCD) such as intrinsic/extrinsic apoptosis and autophagic cell death. The mechanistic study suggested the toxic actions of PCB29-pQ is largely related to its reactive oxygen species (ROS)-generation ability. Pyroptosis is a caspase 1-mediated pro-inflammatory PCD, which was discovered recently. The aim of this study is to seek the linkage between pyroptosis and PCB29-pQ exposures. We first confirmed that PCB29-pQ stimulates Hela cells to produce excess amounts of ROS. Then we found PCB29-pQ activates NOD-like receptor pyrin domain-containing 3 (NLRP3) inflammasome that mediates caspase 1 activation. The activated caspase 1 (cleaved caspase 1) promotes gasdermin D (GSDMD) cleavage and translocation, which facilitates the release of intracellular inflammatory substances by forming membrane hole, ultimately leading cells to pyroptosis. PCB29-pQ-induced high-mobility group box 1 (HMGB1) release and subsequent binding to its receptors [toll-like receptor 2 (TLR2), TLR4, TLR9, and receptor for advanced glycation end products (RAGE)] are essential for the activation of NLRP3 inflammasome. The current study revealed pyroptosis as a new death mode induced by PCB29-pQ, which enriched the understanding of PCBs-induced toxicity and helped to prevent the toxic effects of residual PCBs in the environment.

Latitudinal and Vertical Variation of Synechococcus Assemblage Composition Along 170° W Transect From the South Pacific to the Arctic Ocean.

Synechococcus is one of the most widely distributed and abundant picocyanobacteria in the global oceans. Although latitudinal variation of Synechococcus assemblage in marine surface waters has been observed, few studies compared Synechococcus assemblage composition in surface and subsurface waters at the basin scale. Here, we report marine Synechococcus diversity in the surface and deep chlorophyll maximum (DCM) layers along 170° W from the South Pacific to the Arctic Ocean in summer. Along the transect, spatial niche partitioning of Synechococcus lineages in the surface waters was clearly observed. Species richness of surface Synechococcus assemblage was positively correlated with water temperature. Clade CRD1 was dominant in the areas (15° S-10° N and 35-40° N) associated with upwelling, and there were 3 different subclades with distinct distribution. CRD1-A was restricted in the North Equatorial Current (5-10° N), CRD1-B dominated in the equatorial upwelling region (15° S-0.17° N), and CRD1-C was only distributed in the North Pacific Current (35-40° N). Similarities between the Synechococcus assemblages in the surface and DCM layers were high at the upwelling regions and areas where the mixed layer was deep, while low in the Subtropical Gyres with strong stratification. Clade I, CRD1-B, and CRD1-C were major Synechococcus lineages in the DCM layer. In particular, clade I, which is composed of 7 subclades with distinct thermal niches, was widely distributed in the DCM layer. Overall, our results provide new insights into not only the latitudinal distribution of Synechococcus assemblages, but also their vertical variation in the central Pacific.

Atypical Gasdermin D and Mixed Lineage Kinase Domain-like Protein Leakage Aggravates Tetrachlorobenzoquinone-Induced Nod-like Receptor Protein 3 Inflammasome Activation.

Our previous study showed that tetrachlorobenzoquinone (TCBQ) mediated the activation of Nod-like receptor protein 3 (NLRP3) inflammasome, which involves K+ efflux, reactive oxygen species (ROS) production, and mitochondrial DNA damage. In addition, TCBQ down-regulates NLRP3 ubiquitination and promotes the activation of NLRP3 inflammasome. However, the induction of NLRP3 inflammasome by atypical pathways has not yet been characterized. Using human umbilical vein endothelial cells (HUVEC), we discovered that TCBQ activates caspase 1/4/5 and cleaves gasdermin D (GSDMD) into N-terminal and C-terminal cleavage products. In parallel, TCBQ also activates receptor interacting protein kinase 3 (RIPK3)/mixed lineage kinase domain-like protein (MLKL) signaling pathways. The N-terminal fragments of GSDMD and MLKL translocate from cytoplasm to cell membrane and form oligomers and membrane pores on the cell membrane. The formation of membrane pores not only promotes the extracellular secretion of interleukin 1 beta (IL-1ß) but also affects cellular ion homeostasis, in particular promotes K+ outflow, which further activates NLRP3 inflammasome and aggravates cellular inflammation. These results indicated that GSDMD and MLKL play important roles in TCBQ-induced endothelial pro-inflammatory responses, which may point to potential therapeutic approaches for TCBQ-mediated toxicity.

Tetrachlorobenzoquinone-Induced Nrf2 Confers Neuron-like PC12 Cells Resistance to Endoplasmic Reticulum Stress via Regulating Glutathione Synthesis and Protein Thiol Homeostasis.

Our previous studies demonstrated that tetrachlorobenzoquinone (TCBQ) is toxic to neuron-like cells, which is related to endoplasmic reticulum (ER) stress-induced apoptosis. However, it remains unclear whether TCBQ causes the opening of cellular defense responses. Here we found that activation of nuclear factor erythroid-derived 2-like 2 (Nrf2) triggered an adaptive response against the neurotoxicity induced by TCBQ through the upregulation of intracellular glutathione (GSH) levels in rat pheochromocytoma PC12 cells. TCBQ upregulated the levels of GSH mainly by the following two ways: (i) Nrf2 activation induced the expression of cystine/glutamate antiporter solute carrier family 7 member 11 (SLC7A11, also called xCT); (ii) Nrf2 activation resulted in increased the expression of glutamylcysteine ligase. GSH is involved in cell antioxidant ability and protein thiol homeostasis, especially in the ER. Therefore, GSH has the ability to inhibit ER stress and promote cell survival. Our data showed that decreasing GSH levels exacerbated TCBQ-induced depletion of protein-SH, particularly in the ER. Conversely, increasing GSH levels attenuated TCBQ-induced protein damage, degree of ER stress, and cell death. These findings demonstrated that GSH-inhibited cells were vulnerable to TCBQ-induced ER stress and apoptosis. Overall, our results analyzed the relationships between Nrf2 and ER stress in response to TCBQ and showed that activation of Nrf2-GSH played a protective role against TCBQ-induced ER stress-associated neurotoxicity via regulating GSH synthesis and protein thiol homeostasis.

Polychlorinated Biphenyl Quinones Promotes Breast Cancer Metastasis through Reactive Oxygen Species-Mediated Nuclear Factor κB-Matrix Metalloproteinase Signaling.

It is generally acknowledged that polychlorinated biphenyls (PCBs) exposure increased the incidence of cancer, however, the underlying mechanism(s) of PCBs-induced cancer metastasis are unclear. Although PCBs readily metabolize, little information is available regarding the effect of PCBs metabolites on cancer metastasis. Currently, we evaluate a highly reactive PCBs metabolite, 2,3,5-trichloro-6-phenyl-[1,4]-benzoquinone (PCB29-pQ), relevant to exposure with mammary cancer metastasis. Multiple lines of evidence illustrated that PCB29-pQ induces breast cancer invasion and migration. In particular, this appearance is associated with a two-fold elevation of matrix metalloproteinases-2/-9 (MMP-2/-9) and extracellular nuclear factor kappa B (NF-κB), respectively. Our results clearly demonstrated the translocation of cytosolic NF-κB into the nucleus by a factor of about 2.4. We also revealed the activation of corresponding upstream signaling cascades phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/Akt and p38 and extracellular regulated protein kinases (ERK) mitogen-activated protein kinase (MAPK) by factors of 3.15, 3.09 and 1.69, respectively. Moreover, there was a marked induction of reactive oxygen species (ROS) after a PCB29-pQ challenge and antioxidant treatment that markedly inhibited PCB29-pQ-mediated activation of these axis signaling. Collectively, our result suggested that PCB29-pQ induces breast cancer metastasis via ROS-dependent NF-κB-MMP signaling.

Variation of Synechococcus Pigment Genetic Diversity Along Two Turbidity Gradients in the China Seas.

Synechococcus are important and widely distributed picocyanobacteria that encompass a high pigment diversity. In this study, we developed a primer set (peBF/peAR) for amplifying the cpeBA operon sequence from Synechococcus genomic DNA to study Synechococcus pigment diversity along two turbidity gradients in the China seas. Our data revealed that all previously reported pigment types occurred in the South (SCS) and East (ECS) China Seas. In addition, a novel pigment genetic type (type 3f), represented by the high phycourobilin Synechococcus sp. strain KORDI-100 (Exc495:545 = 2.35), was detected. This pigment genetic type differs from the 3c/3d types not only for a very high PUB/PEB ratio but also for a different intergenic spacer sequence and gene organization of the phycobilisome. Synechococcus of different pigment types exhibited clear niche differentiation. Type 2 dominated in the coastal waters, whereas type 3c/3d and 3f were predominant in oceanic waters of the SCS in summer. In the ECS, however, type 3a was the major pigment type throughout the transect. We suggest that in marine environment, various pigment types often co-occur but with one type dominant and PUB/PEB ratio is related to geographic distribution of Synechococcus pigment types. The two marginal seas of China have markedly different Synechococcus pigment compositions.

Phylogeography and pigment type diversity of Synechococcus cyanobacteria in surface waters of the northwestern pacific ocean.

The widespread unicellular cyanobacteria Synechococcus are major contributors to global marine primary production. Here, we report their abundance, phylogenetic diversity (as assessed using the RNA polymerase gamma subunit gene rpoC1) and pigment diversity (as indirectly assessed using the laterally transferred cpeBA genes, encoding phycoerythrin-I) in surface waters of the northwestern Pacific Ocean, sampled over nine distinct cruises (2008-2015). Abundance of Synechococcus was low in the subarctic ocean and South China Sea, intermediate in the western subtropical Pacific Ocean, and the highest in the Japan and East China seas. Clades I and II were by far the most abundant Synechococcus lineages, the former dominating in temperate cold waters and the latter in (sub)tropical waters. Clades III and VI were also fairly abundant in warm waters, but with a narrower distribution than clade II. One type of chromatic acclimater (3dA) largely dominated the Synechococcus communities in the subarctic ocean, while another (3dB) and/or cells with a fixed high phycourobilin to phycoerythrobilin ratio (pigment type 3c) predominated at mid and low latitudes. Altogether, our results suggest that the variety of pigment content found in most Synechococcus clades considerably extends the niches that they can colonize and therefore the whole genus habitat.

Effect of Subcellular Translocation of Protein Disulfide Isomerase on Tetrachlorobenzoquinone-Induced Signaling Shift from Endoplasmic Reticulum Stress to Apoptosis.

Our previous studies illustrated tetrachlorobenzoquinone (TCBQ)-caused toxicities in neuron-like cells which imply its association with neurodegenerative disorders. Although it is known that TCBQ induces oxidative damage that in turn results in endoplasmic reticulum (ER) stress and apoptosis, it is unclear how TCBQ triggers the signaling switch from pro-survival (to restore cellular homeostasis) to pro-death (trigger apoptosis). Protein disulfide isomerase family proteins (PDIs) regulate the progress of various neurodegenerative disorders, including Parkinson's disease and Alzheimer's disease. We tested the hypothesis that subcellular translocation of PDIs implicates the survival/death signaling switch by inducing mitochondrial outer membrane permeabilization (MOMP). The rat pheochromocytoma PC12 cells were exposed to TCBQ, and the concentration-dependent ER stress was observed upon TCBQ treatment, as indicated by the increase in inositol-requiring kinase/endonuclease 1α (IRE1α) phosphorylation, C/EBP homologous protein (CHOP) expression, X-box-binding protein 1 (XBP1) splicing, and caspase 12 activation. Interestingly, pharmacological (or siRNA) abrogation of PDIA1/PDIA3 aggravated the loss of cell viability induced by the relatively low concentration (10 µM) of TCBQ. However, inhibition of PDIA1/PDIA3 rescued the high concentration (20 µM) of TCBQ-induced cell death. Further mechanistic study illustrated that PDIs initially acted to restore cellular homeostasis to pro-survival but that the constant ER stress promoted the signaling switch to pro-apoptotis by the release of PDIA1/PDIA3 from the ER lumen to induce Bak-dependent MOMP. Our findings suggested that subcellular translocation of PDIs determined the "life or death" fate of PC12 cells to TCBQ-induced oxidative insult.

Quinones Derived from Polychlorinated Biphenyls Induce ROS-Dependent Autophagy by Evoking an Autophagic Flux and Inhibition of mTOR/p70S6k.

Autophagy is a "self-eating" destructive process that eliminates damaged organelles to maintain cellular homeostasis. Polychlorinated biphenyls (PCBs) are one of the most infamous industrial pollutants, which are ubiquitous in nature. In the present study, we found that an active, quinone-type PCB metabolite (PCB29-pQ) treatment causes an autophagic response through mTOR/p70S6k inhibition in HepG2 and MDA-MB-231 cells. Furthermore, our data suggested that PCB29-pQ enhances autophagosome formation through autophagic vacuole (AV) biogenesis, which evokes autophagic flux and induces AV-lysosome colocalization. The inhibition of autophagy enhanced PCB29-pQ-caused cytotoxicity, suggesting that autophagy serves as pro-survival machinery that plays a protective role in the early stage of PCB29-pQ-induced insult. However, higher concentration of PCB29-pQ exposure (>5 µM) caused autophagic cell death, which implied a shift from "pro-survival" to "pro-death" upon autophagic signaling. N-Acetylcysteine suppressed PCB29-pQ-induced autophagy and cytotoxicity, suggesting that ROS plays an important role in the regulation of PCB29-pQ-induced autophagy. Because autophagy shows significant implications in various human diseases and conditions, our current study provides a new mechanism for PCB-associated toxicity.

Tetrachlorobenzoquinone Stimulates NLRP3 Inflammasome-Mediated Post-Translational Activation and Secretion of IL-1ß in the HUVEC Endothelial Cell Line.

Our previous studies suggested that tetrachlorobenzoquinone (TCBQ) elicits pro-inflammatory activities; however, the mechanism of its toxicity toward vascular endothelial cell has not been characterized. Although TCBQ has been shown to stimulate interleukin-1 beta (IL-1ß) expression, it is unknown whether TCBQ regulates post-translational IL-1ß activation. Using human umbilical vein endothelial cells, we discovered that TCBQ not only promotes the expression of NOD-like receptor family, pyrin domain-containing protein 3 (NLRP3) components [composed of NLRP3, adaptor molecule apoptosis-associated speck like protein containing a caspase activation and recruitment domain (ASC), and pro-caspase 1] but also participates in priming the NLRP3 inflammasome. Activation of the NLRP3 inflammasome results in the maturation and release of IL-1ß. Further experiments showed that K(+) efflux, reactive oxygen species (ROS) production, and mitochondrial DNA damage may be involved in NLRP3 inflammasome activation mediated by TCBQ. Moreover, TCBQ downregulates the ubiquitination of NLRP3, further facilitating the activation of the NLRP3 inflammasome. These results suggest that the NLRP3/IL-1ß signaling pathway plays an important role in TCBQ-induced endothelial cell pro-inflammatory responses, which may point to potential therapeutic approaches against TCBQ-mediated toxicity.