Composition and variation of phytoplankton communities during Microcystis bloom in an artificial lagoon of Hangzhou Bay,China

The interaction of various environmental triggers on phytoplankton communities of an artificial lagoon of Hangzhou Bay China, was studied during a Microcystis bloom in summer 2016. Forty-two phytoplankton genera (six phyla) were defined, with Bacillariophyta accounting for half of all phytoplankton genera. It was determined that Melosira, Chlorella, Cyclotella, Microcystis, Merismopedia, Anabaena and Selenastrum, which were identified and counted by an inverted microscope, were the dominant genera. In addition, a series of environmental indicators were analyzed, including salinity, seawater temperature, dissolved inorganic nitrogen, soluble reactive phosphorus (PO₄-P), ammonium (NH₄-N), nitrate nitrogen (NO₃-N), nitrite (NO₂-N), silicate (SiO₄-Si), and chemical oxygen demand of the water samples, as well as zooplankton community. The results of variance partitioning by R language revealed that the most influential factor driving the change in the phytoplankton community was the environment (49.7%), and zooplankton grazing represented only 7.9%. The results of redundancy analysis indicated that the change and composition of the phytoplankton community correlated significantly with the interaction of salinity, PO₄-P, transparency, seawater temperature, and the dominant zooplankton species. Notably, salinity and temperature fluctuation were the key factors inducing the rapid succession of the plankton community in artificial lagoons such as within the Jinshan City Beach (Shanghai, China).

     

水产养殖环境微生物研究进展

近年来,水产养殖产业的迅猛发展在带来巨大经济效益的同时,也使周边水质持续恶化。在水产养殖中,微生物在生态平衡和环境保护方面的作用日益明显。着重介绍了养殖水域菌落结构的持续性变化、微生物在水产养殖中的作用以及水产养殖水域微生物群系组成变化的原因,并阐述了改善养殖水环境的生物修复技术,旨在为水产养殖环境微生物的相关研究及其管理提供参考依据。     

Mechanism and Regulatory Function of CpG Signaling via Scavenger Receptor B1 in Primary B Cells

It is well established that CpG promotes pro-inflammatory cytokine and antibody production by B cells via the Toll-like receptor 9 (TLR9)-dependent pathway. However, scavenger receptors (SRs) are also capable of binding such pathogen-derived molecules, yet their contribution to CpG-induced signaling events has not yet been evaluated. Here we identified a novel TLR9-independent mechanism of CpG-induced signaling and immune function that is mediated by the scavenger B1 receptor (SR-B1). Specifically, we show that CpG/SR-B1 triggers calcium entry into primary B lymphocytes via phospholipase Cγ-1-mediated activation of TRPC3 channels and also B cell adhesion to vascular cell adhesion molecule-1. CpG-induced calcium signals and vascular cell adhesion molecule-1 adhesion are TLR9-independent and are mediated exclusively by SR-B1. Although pro-inflammatory cytokine and Ig production induced by CpG require TLR9 expression, we also found that SR-B1 negatively regulates TLR9-dependent production of interleukin-6, interleukin-10, and IgM. Thus, our results provide a novel perspective on the complexity of CpG signaling within B cells by demonstrating that SR-B1 is an alternative pathway for nucleic acid-induced signaling that provides feedback inhibition on specific TLR9-dependent responses of B cells. Consequently, these results have wide implications for understanding the mechanisms regulating immune tolerance to nucleic acids and pathogen-associated molecules.Stimulus-induced dynamic changes in the concentration of cytoplasmic calcium are primary determinants of the activation, immunological function, and developmental fate of lymphocytes. Calcium signaling through the B cell antigen receptor (BCR)² complex is initiated by the activation of proximal tyrosine kinases Lyn and Syk, which phosphorylate the adaptor BLNK to facilitate its association with and activation of PLCγ-2. PLCγ2 hydrolyzes phosphatidylinositol 4,5-bisphosphate into diacylglycerol and 1,4,5-inositol trisphosphate (IP₃) (for review see Ref. 1), which activates IP₃ receptor/channels that mediate Ca²⁺ release from endoplasmic reticulum into the cytosol (2) (for review see Refs. 3, 4). Ca²⁺ release from endoplasmic reticulum stores and the resulting depletion of Ca²⁺ (not an increase in cytoplasmic [Ca²⁺]) are the central and prerequisite events required to activate plasma membrane “store-operated” calcium release-activated calcium (CRAC) channels.CRAC channels are responsible for antigen receptor-triggered calcium entry; however, a growing body of evidence suggests that CRAC channels do not underlie all the diverse calcium-regulated responses of lymphocytes, particularly those triggered by innate stimuli. For example, we previously identified several calcium-permeant non-selective cation channels (NSCCs) that are uniquely activated by distinct arachidonic acid-derived (eicosanoid) inflammatory mediators and by mechanical stimuli (5–7). Thus, multiple calcium-permeant channels with distinct activation mechanisms may underlie stimulus-specific calcium-dependent B cell functions in vivo. Surprisingly, a number of pathogen-associated Toll-like receptor agonists are known to be strong B cell mitogens, yet the potential for calcium-dependent signaling functions by these polyclonal B cell mitogens has not yet been fully evaluated.Studies detailed in this report focus on the mechanism of calcium signaling elicited by unmethylated CpG DNA in primary B cells. Unmethylated CpG DNA is typically considered a pathogen-derived molecule that triggers polyclonal B cell activation, cytokine production, and immunoglobulin production via Toll-like receptor 9 (TLR9) engagement (8, 9). Because CpG induces a subset of the B cell responses normally elicited by cognate antigen binding to the BCR complex, we asked whether CpG stimulation mobilizes calcium. We found that while CpG stimulation and BCR engagement both elicit similar biphasic calcium signals, CpG-mediated calcium entry is regulated by TRPC3, a calcium-permeant NSCC of the canonical transient receptor potential (TRPC) channel family (10) and that, unlike the BCR, which couples to calcium entry via PLCγ-2, TRPC3 activation involves an adaptor like function of PLCγ-1.We also report that CpG-mediated calcium signals are initiated by the scavenger receptor B1 (SR-B1) independently of TLR9. To our knowledge, this is the first demonstration of SR-B1 function in B lymphocytes; although scavenger receptors have been implicated in the responses of other immune cells. For example, bacterial pathogens and byproducts of apoptotic cells contribute to the pathogenesis of immune-mediated diseases, including lupus in part via MARCO and CD36 expressed by marginal zone macrophages (11). In naïve B cells, CD36 expression is largely restricted to marginal zone cells. Notably, CD36 cooperates with TLR2 to produce antibodies against phosphocholine, which is an endogenous antigen (13). Given our finding that CpG elicits calcium signals via SR-B1 on lymphocytes, we asked whether SR-B1 might also act cooperatively, in this case with TLR9, to trigger inflammatory responses of B cells. In fact, our results indicate that SR-B1 negatively regulates CpG/TLR9-mediated production of specific immunoglobulins (IgM) and pro-inflammatory cytokines (IL-6 and IL-10) by B cells. These findings have important implications for understanding how calcium is regulated in B cells, but also point to novel mechanisms by which pathogen-associated molecules regulate B cell activation.     

The WAVE2 complex regulates actin cytoskeletal reorganization and CRAC-mediated calcium entry during T cell activation

BACKGROUND: The engagement of the T cell receptor results in actin cytoskeletal reorganization at the immune synapse (IS) and the triggering of biochemical signaling cascades leading to gene regulation and, ultimately, cellular activation. Recent studies have identified the WAVE family of proteins as critical mediators of Rac1-induced actin reorganization in other cell types. However, whether these proteins participate in actin reorganization at the IS or signaling pathways in T cells has not been investigated. RESULTS: By using a combination of biochemical, genetic, and cell biology approaches, we provide evidence that WAVE2 is recruited to the IS, is biochemically modified, and is required for actin reorganization and beta-integrin-mediated adhesion after TCR crosslinking. Moreover, we show that WAVE2 regulates calcium entry at a point distal to PLCgamma1 activation and IP(3)-mediated store release. CONCLUSIONS: These data reveal a role for WAVE2 in regulating multiple pathways leading to T cell activation. In particular, this work shows that WAVE2 is a key component of the actin regulatory machinery in T cells and that it also participates in linking intracellular calcium store depletion to calcium release-activated calcium (CRAC) channel activation.     

Mechanisms of hypotonicity-induced calcium signaling and integrin activation by arachidonic acid-derived inflammatory mediators in B cells

We previously characterized the initial steps in the activation of novel (calcium-permeant) nonselective cation channels (NSCCs) and calcium release-activated calcium channels in primary murine B lymphocytes. Phospholipase C products, namely diacylglycerol and d-myo-inositol 1,4,5-trisphosphate, were identified as proximal intracellular agonists of these respective channels following mechanical stimulation of B cells. However, neither the distal steps in NSCC activation nor the contribution of these channels to sustained mechanical signaling were defined in these previous studies. In this study, single cell measurements of intracellular Ca(2+) were used to define the mechanisms of NSCC activation and demonstrate a requirement for arachidonic acid liberated from diacylglycerol. Several arachidonic acid-derived derivatives were identified that trigger Ca(2+) entry into B cells, including the lipoxygenase product 5-hydroperoxyeicosatetranenoic acid and the cytochrome P450 hydroxylase product 20-hydroxyeicosatetraenoic; however, the cytochrome P450 epoxygenase product 5,6-epoxyeicosatrienoic acid is primarily responsible for hypotonicity-induced responses. In addition to regulating calcium entry, our data suggest that eicosanoid-activated NSCCs have a separate and direct role in regulating the avidity of integrins on B cells for extracellular matrix proteins, including ICAM-1 and VCAM-1. Thus, in addition to defining a novel osmotically activated signal transduction pathway in B cells, our results have broad implications for understanding how inflammatory mediators dynamically and rapidly regulate B cell adhesion and trafficking.     

Monoallelic expression and asynchronous replication of p120 catenin in mouse and human cells

The number of autosomal mammalian genes subject to random monoallelic expression has been limited to genes highly specific to the function of chemosensory neurons or lymphocytes, making this phenomenon difficult to address systematically. Here we demonstrate that asynchronous DNA replication can be used as a marker for the identification of novel genes with monoallelic expression and identify p120 catenin, a gene involved in cell adhesion, as belonging to this class. p120 is widely expressed; its presence in available cell lines allowed us to address quantitative aspects of monoallelic expression. We show that the epigenetic choice of active allele is clonally stable and that biallelic clones express p120 at twice the level of monoallelic clones. Unlike previous reports about genes of this type, we found that expression of p120 can be monoallelic in one cell type and strictly biallelic in another. We show that in human lymphoblasts, the silencing of one allele is incomplete. These unexpected properties are likely to be wide-spread, as we show that the Tlr4 gene shares them. Identification of monoallelic expression of a nearly ubiquitous gene indicates that this type of gene regulation is more common than previously thought. This has important implications for carcinogenesis and definition of cell identity.     

Comparative study on mitogenomes of green tide algae

Since 2007, the annual green tide disaster in the Yellow Sea has brought serious economic losses to China. There is no research on the genetic similarities of four constituent species of green tide algae at the genomic level. We previously determined the mitochondrial genomes of Ulva prolifera, Ulva linza and Ulva flexuosa. In the present work, the mitochondrial genome of another green tide (Ulva compressa) was sequenced and analyzed. With the length of 62,311 bp, it contained 29 encoding genes, 26 tRNAs and 10 open reading frames. By comparing these four mitochondrial genomes, we found that U. compressa was quite different from the other three types of Ulva species. However, there were similarities between U. prolifera and U. linza in the number, distribution and homology of open reading frames, evolutionary and codon variation of tRNA, evolutionary relationship and selection pressure of coding genes. Repetitive sequence analysis of simple sequence repeats, tandem repeat and forward repeats further supposed that they have evolved from the same origin. In addition, we directly analyzed gene homologies and translocation of four green tide algae by Mauve alignment. There were gene order rearrangements among them. With fast-evolving genomes, these four green algal mitochondria have both conservatism and variation, thus opening another window for the understanding of origin and evolution of Ulva.