植物病原丝状真菌寄生性与RGS蛋白的关系研究

以49个全基因组序列已经公布的真菌为研究对象,通过OrthoVenn2同源基因簇比对、BLASTp比对和关键词搜索3种方法对G蛋白信号调控因子（regulators of G-protein signaling,RGS）同源基因进行比对分析,并结合SMART进行保守结构域分析,结果发现,49个真菌中共有229个RGS蛋白,每种真菌中所含有RGS蛋白的数量范围为3~9个,且死体营养型病原菌和半活体营养型病原菌的RGS蛋白数量高于活体营养型病原菌;根据RGS蛋白中保守结构域进行分类,可以划分为DEP-RGS、RGS-TM、PXA-RGS-PX、RGS、RGS-PAS-PAC、TM-RGS等6种,其中,具有RGS-PAS-PAC和TM-RGS这2种特殊保守结构域的RGS蛋白主要集中在半活体营养型病原菌和死体营养型病原菌;进一步对229个RGS蛋白进行遗传关系分析,发现具有同种保守结构域的RGS蛋白亲缘关系较近。上述研究结果表明植物病原丝状真菌的寄生性与RGS蛋白数量和种类之间存在着一定的关联性。     

A bacterial toxin that controls cell cycle progression as a deoxyribonuclease I-like protein

Many bacterial pathogens encode a multisubunit toxin, termed cytolethal distending toxin (CDT), that induces cell cycle arrest, cytoplasm distention, and, eventually, chromatin fragmentation and cell death. In one such pathogen, Campylobacter jejuni, one of the subunits of this toxin, CdtB, was shown to exhibit features of type I deoxyribonucleases. Transient expression of this subunit in cultured cells caused marked chromatin disruption. Microinjection of low amounts of CdtB induced cytoplasmic distention and cell cycle arrest. CdtB mutants with substitutions in residues equivalent to those required for catalysis or magnesium binding in type I deoxyribonucleases did not cause chromatin disruption. CDT holotoxin containing these mutant forms of CdtB did not induce morphological changes or cell cycle arrest.     

植物细胞壁蛋白质提取方法的改进

以玉米黄化苗的中胚轴为材料,利用盐分级分离细胞壁蛋白质.主要做了2点改进:1)利用超声波破碎植物组织细胞;2)增加苯酚抽提步骤除去可溶性细胞质蛋白、细胞壁蛋白质的回收及脱盐.整个过程不涉及过柱层析和透析步骤,因而缩短了提取时间,提高了细胞壁蛋白质的产率.     

Vacuolar processing enzyme positively modulates plant resistance and cell death in response to Phytophthora parasitica infection

Oomycete, particularly Phytophthora species, causes the most devastating crop diseases, such as potato late blight,and threatens the sustainable crop production worldwide. Our previous studies identified Resistance to Phytophthora parasitica 1(RTP1) as a negative regulator of Arabidopsis resistance to multiple biotrophic pathogens and RTP1 lossof-function plants displayed rapid cell death and reactive oxygen species(ROS) production during early colonization of P. parasitica. In this study, we ai...     

The ribosome modulates nascent protein folding

Proteins are synthesized by the ribosome and generally must fold to become functionally active. Although it is commonly assumed that the ribosome affects the folding process, this idea has been extremely difficult to demonstrate. We have developed an experimental system to investigate the folding of single ribosome-bound stalled nascent polypeptides with optical tweezers. In T4 lysozyme, synthesized in a reconstituted in vitro translation system, the ribosome slows the formation of stable tertiary interactions and the attainment of the native state relative to the free protein. Incomplete T4 lysozyme polypeptides misfold and aggregate when free in solution, but they remain folding-competent near the ribosomal surface. Altogether, our results suggest that the ribosome not only decodes the genetic information and synthesizes polypeptides, but also promotes efficient de novo attainment of the native state.     

RacA,a bacterial protein that anchors chromosomes to the cell poles

Eukaryotic chromosomes are anchored to a spindle apparatus during mitosis, but no such structure is known during chromosome segregation in bacteria. When sister chromosomes are segregated during sporulation in Bacillus subtilis, the replication origin regions migrate to opposite poles of the cell. If and how origin regions are fastened at the poles has not been determined. Here we describe a developmental protein, RacA, that acts as a bridge between the origin region and the cell poles. We propose that RacA assembles into an adhesive patch at a centromere-like element near the origin, causing chromosomes to stick at the poles.     

A nodule-specific plant protein (nodulin-35) from soybean

Nodulin-35, a 35,000-molecular-weight protein, is present in soybean root nodules developed by different strains of Rhizobium japonicum, irrespective of their effectiveness in fixing atmospheric nitrogen. This protein is not detected in uninfected plants and bacteroids or in free-living Rhizobium and appears to be synthesized by the plant during the formation of root nodules.     

A fluoroquinolone resistance protein from Mycobacterium tuberculosis that mimics DNA

Fluoroquinolones are gaining increasing importance in the treatment of tuberculosis. The expression of MfpA, a member of the pentapeptide repeat family of proteins from Mycobacterium tuberculosis, causes resistance to ciprofloxacin and sparfloxacin. This protein binds to DNA gyrase and inhibits its activity. Its three-dimensional structure reveals a fold, which we have named the right-handed quadrilateral beta helix, that exhibits size, shape, and electrostatic similarity to B-form DNA. This represents a form of DNA mimicry and explains both its inhibitory effect on DNA gyrase and fluoroquinolone resistance resulting from the protein's expression in vivo.     

A metalloprotease disintegrin that controls cell migration in Caenorhabditis elegans

In Caenorhabditis elegans, the gonad acquires two U-shaped arms by the directed migration of its distal tip cells (DTCs) along the body wall basement membranes. Correct migration of DTCs requires the mig-17 gene, which encodes a member of the metalloprotease-disintegrin protein family. The MIG-17 protein is secreted from muscle cells of the body wall and localizes in the basement membranes of gonad. This localization is dependent on the disintegrin-like domain of MIG-17 and its catalytic activity. These results suggest that the MIG-17 metalloprotease directs migration of DTCs by remodeling the basement membrane.     

A sperm cytoskeletal protein that signals oocyte meiotic maturation and ovulation

Caenorhabditis elegans oocytes, like those of most animals, arrest during meiotic prophase. Sperm promote the resumption of meiosis (maturation) and contraction of smooth muscle-like gonadal sheath cells, which are required for ovulation. We show that the major sperm cytoskeletal protein (MSP) is a bipartite signal for oocyte maturation and sheath contraction. MSP also functions in sperm locomotion, playing a role analogous to actin. Thus, during evolution, MSP has acquired extracellular signaling and intracellular cytoskeletal functions for reproduction. Proteins with MSP-like domains are found in plants, fungi, and other animals, suggesting that related signaling functions may exist in other phyla.     

Recent advances in plant immunity with cell death: A review

Cell death is an important physiological phenomenon in life. It can be programmed or unprogrammed. Unprogrammed cell death is usually induced by abiotic or biotic stress. Recent studies have shown that many proteins regulate both cell death and immunity in plants. Here, we provide a review on the advances in plant immunity with cell death, especially the molecular regulation and underlying mechanisms of those proteins involved in both cell death and plant immunity. In addition, we discuss potential approaches toward improving plant immunity without compromising plant growth.     

A LAT mutation that inhibits T cell development yet induces lymphoproliferation

Mice homozygous for a single tyrosine mutation in LAT (linker for activation of T cells) exhibited an early block in T cell maturation but later developed a polyclonal lymphoproliferative disorder and signs of autoimmune disease. T cell antigen receptor (TCR)-induced activation of phospholipase C-gamma1 (PLC-gamma1) and of nuclear factor of activated T cells, calcium influx, interleukin-2 production, and cell death were reduced or abrogated in T cells from LAT mutant mice. In contrast, TCR-induced Erk activation was intact. These results identify a critical role for integrated PLC-gamma1 and Ras-Erk signaling through LAT in T cell development and homeostasis.     

新型生物农药——植物激活蛋白的应用效果研究

植物激活蛋白的有效成分是从微生物中分离提取的一种高活性蛋白,无毒、无害、无污染。近年来,这种新型的植物激活蛋白农药,已分别在水稻、辣椒、大白菜、藠头、烟草、棉花、柑桔等作物上进行了试验示范。结果表明,植物激活蛋白1000倍液连续施用3~4次,对多种农作物主要病害都具有一定的诱抗作用,特别是对病毒病的诱抗效果较好,同时能明显促进作物的生长发育,提高作物的产量和品质。     

植物多聚半乳糖醛酸酶抑制蛋白研究进展

多聚半乳糖醛酸酶抑制蛋白(PGIP)是一种特异性结合并抑制真菌内切多聚半乳糖醛酸酶活性的细胞壁结合蛋白,迄今已在20多种植物体内发现了多聚半乳糖醛酸酶抑制蛋白。综述了国内外近几年有关PGIP基因研究、PGIP在植物抗病中的作用以及在抗病育种中应用的研究成果。     

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.     

Antibodies to human c-myc oncogene product: evidence of an evolutionarily conserved protein induced during cell proliferation

Antisera to a synthetic c-myc peptide and to c-myc antigens synthesized from various portions of the human gene expressed in Escherichia coli were used in order to characterize the protein product of the human c-myc oncogene. Although the deduced molecular weight of the human c-myc protein is 49,000, these antisera precipitate a protein from human cells that migrates in sodium dodecyl sulfate-polyacrylamide gel as if its molecular weight were 65,000. In addition, the mouse c-myc protein, whether synthesized in cells or in a cell-free system directed by pure, synthetic messenger RNA, has analogous properties and is immunoprecipitated by the antiserum to the human c-myc protein. Similar proteins are immunoprecipitated from monkey, rat, hamster, and frog cells, suggesting evolutionary conservation of antigenic structure of the c-myc protein among vertebrates. In addition, and in a manner consistent with the behavior of its messenger RNA, the immunoprecipitable c-myc protein is sharply induced by the action of mitogens on resting human T cells.