Neuronal controls of a behavioral response mediated by the abdominal ganglion of Aplysia

Tactile stimulation of the siphon and mantle shelf in Aplysia causes a characteristic withdrawal response of the external organs of the mantle cavity. A similar response also occurs spontaneously. Both responses are mediated by the abdominal ganglion and therefore provide an opportunity for correlating cellular functioning and behavior in a relatively simple and well-studied neuronal system. The withdrawal responses are controlled by five identified motor cells which receive two types of synaptic inputs. One set of excitatory connections, activated by tactile stimulation of the siphon and mantle shelf, mediates the defensive withdrawal reflex. A second set of connections is activated by a spontaneous burst of activity in a group of closely coupled interneurons which are excitatory to some of the motor cells and inhibitory to the others. This second set of connections mediates the spontaneous withdrawal response. These two inputs can therefore switch the same population of motor cells from a simple reflex to a more complex, internally organized response.     

The unfolded protein response: from stress pathway to homeostatic regulation

The vast majority of proteins that a cell secretes or displays on its surface first enter the endoplasmic reticulum (ER), where they fold and assemble. Only properly assembled proteins advance from the ER to the cell surface. To ascertain fidelity in protein folding, cells regulate the protein-folding capacity in the ER according to need. The ER responds to the burden of unfolded proteins in its lumen (ER stress) by activating intracellular signal transduction pathways, collectively termed the unfolded protein response (UPR). Together, at least three mechanistically distinct branches of the UPR regulate the expression of numerous genes that maintain homeostasis in the ER or induce apoptosis if ER stress remains unmitigated. Recent advances shed light on mechanistic complexities and on the role of the UPR in numerous diseases.     

A bacterial virulence protein suppresses host innate immunity to cause plant disease

Plants have evolved a powerful immune system to defend against infection by most microbial organisms. However, successful pathogens, such as Pseudomonas syringae, have developed countermeasures and inject virulence proteins into the host plant cell to suppress immunity and cause devastating diseases. Despite intensive research efforts, the molecular targets of bacterial virulence proteins that are important for plant disease development have remained obscure. Here, we show that a conserved P. syringae virulence protein, HopM1, targets an immunity-associated protein, AtMIN7, in Arabidopsis thaliana. HopM1 mediates the destruction of AtMIN7 via the host proteasome. Our results illustrate a strategy by which a bacterial pathogen exploits the host proteasome to subvert host immunity and causes infection in plants.     

Innate immunity in Caenorhabditis elegans is regulated by neurons expressing NPR-1/GPCR

A large body of evidence indicates that metazoan innate immunity is regulated by the nervous system, but the mechanisms involved in the process and the biological importance of such control remain unclear. We show that a neural circuit involving npr-1, which encodes a G protein-coupled receptor (GPCR) related to mammalian neuropeptide Y receptors, functions to suppress innate immune responses. The immune inhibitory function requires a guanosine 3',5'-monophosphate-gated ion channel encoded by tax-2 and tax-4 as well as the soluble guanylate cyclase GCY-35. Furthermore, we show that npr-1- and gcy-35-expressing sensory neurons actively suppress immune responses of nonneuronal tissues. A full-genome microarray analysis on animals with altered neural function due to mutation in npr-1 shows an enrichment in genes that are markers of innate immune responses, including those regulated by a conserved PMK-1/p38 mitogen-activated protein kinase signaling pathway. These results present evidence that neurons directly control innate immunity in C. elegans, suggesting that GPCRs may participate in neural circuits that receive inputs from either pathogens or infected sites and integrate them to coordinate appropriate immune responses.     

Proapoptotic BAX and BAK modulate the unfolded protein response by a direct interaction with IRE1alpha

Accumulation of misfolded protein in the endoplasmic reticulum (ER) triggers an adaptive stress response-termed the unfolded protein response (UPR)-mediated by the ER transmembrane protein kinase and endoribonuclease inositol-requiring enzyme-1alpha (IRE1alpha). We investigated UPR signaling events in mice in the absence of the proapoptotic BCL-2 family members BAX and BAK [double knockout (DKO)]. DKO mice responded abnormally to tunicamycin-induced ER stress in the liver, with extensive tissue damage and decreased expression of the IRE1 substrate X-box-binding protein 1 and its target genes. ER-stressed DKO cells showed deficient IRE1alpha signaling. BAX and BAK formed a protein complex with the cytosolic domain of IRE1alpha that was essential for IRE1alpha activation. Thus, BAX and BAK function at the ER membrane to activate IRE1alpha signaling and to provide a physical link between members of the core apoptotic pathway and the UPR.     

alphaE-catenin controls cerebral cortical size by regulating the hedgehog signaling pathway

During development, cells monitor and adjust their rates of accumulation to produce organs of predetermined size. We show here that central nervous system-specific deletion of the essential adherens junction gene, alphaE-catenin, causes abnormal activation of the hedgehog pathway, resulting in shortening of the cell cycle, decreased apoptosis, and cortical hyperplasia. We propose that alphaE-catenin connects cell-density-dependent adherens junctions with the developmental hedgehog pathway and that this connection may provide a negative feedback loop controlling the size of developing cerebral cortex.     

Unfolded proteins are Ire1-activating ligands that directly induce the unfolded protein response

The unfolded protein response (UPR) detects the accumulation of unfolded proteins in the endoplasmic reticulum (ER) and adjusts the protein-folding capacity to the needs of the cell. Under conditions of ER stress, the transmembrane protein Ire1 oligomerizes to activate its cytoplasmic kinase and ribonuclease domains. It is unclear what feature of ER stress Ire1 detects. We found that the core ER-lumenal domain (cLD) of yeast Ire1 binds to unfolded proteins in yeast cells and to peptides primarily composed of basic and hydrophobic residues in vitro. Mutation of amino acid side chains exposed in a putative peptide-binding groove of Ire1 cLD impaired peptide binding. Peptide binding caused Ire1 cLD oligomerization in vitro, suggesting that direct binding to unfolded proteins activates the UPR.     

激发子诱导的过敏性细胞死亡调控基因的筛选

采用病毒诱导基因沉默技术从本氏烟(Nicotiana benthamiana)cDNA文库中筛选受3种不同激发子(Nep1、harpin和INF1)诱导的过敏性细胞死亡的调控基因。以农杆菌Gv3101为宿主、利用PVX病毒表达载体构建了含有7 000个单克隆的本氏烟cDNA文库,采用牙签刺伤法和注射接种法,从6 000个克隆中筛选到了34个能使激发子诱发的过敏性细胞死亡表型发生改变的克隆。对上述阳性克隆进行序列测定和分析,发现其中13个与已知的基因具有较高的同源性,其中克隆Nb14-4编码1个特异的ALY蛋白;克隆Nb3-9和Nb4-26分别编码1个苹果酸脱氢酶和果糖二磷酸醛缩酶;Nb4-28编码普通烟草中的14-3-3 d-2蛋白。还有21个克隆在公共数据库中没有同源基因。上述结果表明:利用病毒表达载体建立cDNA文库,并采用病毒诱导基因沉默技术可从烟草全基因组内筛选受不同激发子诱导的过敏性细胞死亡的调控基因,为揭示植物过敏性细胞死亡分子机制提供试验依据。     

ALV-J下调鸡MARCO转录水平拮抗宿主抗病毒天然免疫应答的研究

为研究鸡巨噬细胞受体(MARCO)基因与J亚群禽白血病病毒(ALV-J)感染两者间的关联,先过表达ALV-J env基因不同结构域后通过RT-qPCR检测MARCO基因mRNA的转录水平,再构建MARCO真核表达载体并转染HD11细胞,通过RT-qPCR和Western blot检测MARCO过表达对ALV-J复制水平...     

Regulation of the polarity protein Par6 by TGFbeta receptors controls epithelial cell plasticity

The transition of cells from an epithelial to a mesenchymal phenotype is a critical event during morphogenesis in multicellular organisms and underlies the pathology of many diseases, including the invasive phenotype associated with metastatic carcinomas. Transforming growth factor beta (TGFbeta) is a key regulator of epithelial-to-mesenchymal transition (EMT). However, the molecular mechanisms that control the dissolution of tight junctions, an early event in EMT, remain elusive. We demonstrate that Par6, a regulator of epithelial cell polarity and tight-junction assembly, interacts with TGFbeta receptors and is a substrate of the type II receptor, TbetaRII. Phosphorylation of Par6 is required for TGFbeta-dependent EMT in mammary gland epithelial cells and controls the interaction of Par6 with the E3 ubiquitin ligase Smurf1. Smurf1, in turn, targets the guanosine triphosphatase RhoA for degradation, thereby leading to a loss of tight junctions. These studies define how an extracellular cue signals to the polarity machinery to control epithelial cell morphology.     

Antiallergic drug cromolyn may inhibit histamine secretion by regulating phosphorylation of a mast cell protein

Cromolyn inhibited histamine release from mast cells that was induced by a classic secretagogue and correspondingly increased incorporation of radioactive phosphate into a 78,000-dalton protein. These effects on histamine secretion and on protein phosphorylation were rapid in onset and both showed tachyphylaxis. Cromolyn may therefore act by altering the phosphorylation of a protein involved in the regulation of secretion.     

The substrate of Greatwall kinase, Arpp19, controls mitosis by inhibiting protein phosphatase 2A

Initiation and maintenance of mitosis require the activation of protein kinase cyclin B-Cdc2 and the inhibition of protein phosphatase 2A (PP2A), which, respectively, phosphorylate and dephosphorylate mitotic substrates. The protein kinase Greatwall (Gwl) is required to maintain mitosis through PP2A inhibition. We describe how Gwl activation results in PP2A inhibition. We identified cyclic adenosine monophosphate-regulated phosphoprotein 19 (Arpp19) and α-Endosulfine as two substrates of Gwl that, when phosphorylated by this kinase, associate with and inhibit PP2A, thus promoting mitotic entry. Conversely, in the absence of Gwl activity, Arpp19 and α-Endosulfine are dephosphorylated and lose their capacity to bind and inhibit PP2A. Although both proteins can inhibit PP2A, endogenous Arpp19, but not α-Endosulfine, is responsible for PP2A inhibition at mitotic entry in Xenopus egg extracts.     

ELISA 法检测干旱下花生不同品种中AhNCED1 蛋白表达变化

ABA合成关键酶Ah NCED1与花生抗旱性相关。优化ELISA法检测花生Ah NCED1蛋白体系,利用该体系检测不同产地7个花生品种幼苗干旱处理24h后叶片内Ah NCED1蛋白表达变化。结果表明,正常生长条件下,7个品种Ah NCED1蛋白表达量呈现较低水平,品种间无显著性差异;干旱24h后,所有品种的Ah NCED1蛋白表达量显著增加;Ah NCED1蛋白表达变化倍数从大到小依次是:中花16濮花28花育19福花4中花6花育33海花1,与QPCR检测Ah NCED1基因表达和Westernblot的检测结果比较一致。综合分析3种方法检测不同品种的Ah NCED1基因和蛋白结果表明,ELISA法及QPCR配合使用适用于大范围的快速筛选抗旱花生品种,为抗旱花生品种筛选提供技术支撑。     

The putative elongator complex protein Elp3 is involved in asexual development and pathogenicity by regulating autophagy in the rice blast fungus

Autophagy is responsible for maintaining fundamental cellular homeostasis and is, therefore, essential for diverse development processes. This study reported that PoElp3, the putative catalytic subunit of Elongator complex, is involved in the maintenance of autophagy homeostasis to facilitate asexual development and pathogenicity in the rice blast fungus Pyricularia oryzae. It was found that the ΔPoelp3 strains were defective in vegetative growth, conidiation, stress response, and pathogenicity. The mutants exhibited hyper-activated autophagy in the vegetative hyphae under both nutrient-rich and nutrient-deficient conditions. The hyper-activation of autophagy possibly suppressed the production of vegetative hyphae in the ΔPoelp3 strains. Moreover, the ΔPoelp3 strains were found to be more sensitive to rapamycin during vegetative- and invasive-hyphal growth but have no effect on Target-of-Rapamycin (TOR) signaling inhibition. Taken together, these results demonstrated that PoElp3 is involved in asexual development and pathogenicity by regulating autophagy in the rice blast fungus.     

OsMas1, a novel maspardin protein gene,confers tolerance to salt and drought stresses by regulating ABA signaling in rice

Drought and salt stresses, the major environmental abiotic stresses in agriculture worldwide, affect plant growth, crop productivity, and quality. Therefore, developing crops with higher drought and salt tolerance is highly desirable. This study reported the isolation, biological function, and molecular characterization of a novel maspardin gene, OsMas1, from rice. The OsMas1 protein was localized to the cytoplasm. The expression levels of OsMas1 were up-regulated under mannitol, PEG6000, NaCl, ...     

Expression and functional analyses of the mitogen-activated protein kinase(MPK) cascade genes in response to phytohormones in wheat (Triticum aestivum L.)

Mitogen-activated protein kinase(MPK) cascades consist of a set of kinase types(MPKKKs,MPKKs,MPKs) to establish conserved signal-transducing modules mediating plant growth,development as well as responses to internal and external cues.In this study,the expression patterns of six MPKKK,two MPKK,and 11 MPK genes in wheat in responses to external treatments of phytohormones,including naphthylacetic acid(NAA),abscisic acid(ABA),6-benzyladenine(6-BA),gibberellin(GA_3),salisylic acid(SA),jasmonic acid(JA),and ethylene(ETH),were investigated.Expression analysis revealed that several of the MPK cascade genes are responses to the external phytohormone signaling.Of which,TaMPKKKA;3is induced by 6-BA and NAA while TaMPK4 repressed by ETH,GA_3,SA,and JA;TaMPKKKA,TaMPKKKA;3 and TaMPK1 are down-regulated by ETH and GA_3whereas TaMPK9 and TaMPK12 repressed by ETH and JA in addition that TaMPK12 also repressed by GA_3;TaMPK12;1 is down-regulated by ABA,GA_3 and SA while TaMPK17 repressed by all exogenous phytonormones examined.TaMPK4,a MPK type gene previously characterized to mediate tolerance to phosphate(Pi)deprivation,was functionally evaluated for its role in mediation of responses of plants to exogenous GA_3,ETH,SA,and JA.Results indicated that overexpression and antisense expression of TaMPK4 in tobacco dramatically modify the growth of seedlings upon treatments of GA_3,SA and JA,in which the overexpressors behaved deteriorated growth feature whereas the seedlings with antisense expression of TaMPK4 exhibited improved seedling phenotype.The growth behaviors in lines overexpressing or antisensely expressing TaMPK4 are closely associated with the biomass and the corresponding hormone-associated parameters.These results demonstrated that TaMPK4 acts as a critical player in mediating the phytohormone signaling.Our findings have identified the phytohormone-responsive MPK cascade genes in wheat and provided a connection between the phytohormone-mediated responses and the MPK cascade pathways.