芸薹属自交不亲和功能因子及分子机制研究进展

芸薹属的自交不亲和性受S位点基因控制,其上的SRK基因和SCR/SP11基因是自交不亲和反应中的两个关键因子,另外所发现的其他因子也对自交不亲和发挥了重要作用。文章介绍了影响自交不亲和的功能因子及其分子结构特征和功能,对自交不亲和反应的分子机制作了进一步阐述,同时对这些功能基因在芸薹属植物甘蓝染色体组上的定位研究作出展望。     

甘蓝自交不亲和细胞信号转导的功能基因研究进展

自交不亲和性是开花植物防止近亲繁殖而广泛存在的一种遗传屏障,在育种工作中意义重大,它在遗传上受一个带有复等位基因的多态性S基因座所控制。本文综述了近年来在甘蓝自交不亲和信号转导途径中相关功能基因的研究进展。SRK基因和SP11/SCR基因是控制甘蓝自交不亲和性的两个关键因子。SRK基因是雌蕊柱头中自交不亲和反应的专一决定因子,编码SP11/SCR基因的蛋白在花药壁和花粉中特异表达。编码SLG基因的蛋白在自交不亲和反应中起增强SRK活性的作用。另外也对信号传导途径中下游蛋白质的作用模式作了展望。     

Recognition and rejection of self in plant reproduction

Plant self-incompatibility (SI) systems are unique among self/nonself recognition systems in being based on the recognition of self rather than nonself. SI in crucifer species is controlled by highly polymorphic and co-evolving genes linked in a complex. Self recognition is based on allele-specific interactions between stigma receptors and pollen ligands that result in the arrest of pollen tube development. Commonalities and differences between SI and other self/nonself discrimination systems are discussed.     

Phylogenetic Analysis on SLG and SRK Genes in Brassica and Raphanus

S-locus genes were cloned from three Brassica napus and three B. campestris lines by using PCR walking and homologue sequence methods. A phylogenetic gene tree was constructed based on the six cloned genes and fifty-one previously reported SLG/SRK genes of Brassica and Raphanus. The SLGs from R. sativus were dispersed in the phylogenetic tree intermingling with SLG/SRKs from B. oleracea, B. napus and B. campestris. The SLG/SRK genes of class Ⅱ clustered independently in one group. The SLG/SRK genes of class Ⅰ showed to be more divergent than class Ⅱ genes. These results suggested that the divergence of class Ⅰ and class Ⅱ should have occurred before the differentiation of the genera Brassica and Raphanus. In addition, SLG and SRK of the same S haplotypes belonged to the same class. It suggested that class-Ⅰ and class-Ⅱ group divergence occurred first, and then SLG and SRK diverged. The three SC SRK genes from B. napus and B. campestris were grouped into one cluster, displaying difference from the SC SLG of B.oleracea. These three SC SRK genes were close to SI SRK of SI1300, SI271 and guanyou in phylogenetic relationships.These results indicated that SC and SI genes diverged more recently. It is not clear yet whether the differentiation of SC and SI genes was earlier than the differentiation of Brassica and Raphanus. Studies based on more genes are necessary for a comprehensive elucidation of the phylogenetic relationships in Brassicaceae.     

Nonmethylated transposable elements and methylated genes in a chordate genome

The genome of the invertebrate chordate Ciona intestinalis was found to be a stable mosaic of methylated and nonmethylated domains. Multiple copies of an apparently active long terminal repeat retrotransposon and a long interspersed element are nonmethylated and a large fraction of abundant short interspersed elements are also methylation free. Genes, by contrast, are predominantly methylated. These data are incompatible with the genome defense model, which proposes that DNA methylation in animals is primarily targeted to endogenous transposable elements. Cytosine methylation in this urochordate may be preferentially directed to genes.     

Evidence for karyogamy and exchange of genetic material in the binucleate intestinal parasite Giardia intestinalis

The diplomonad parasite Giardia intestinalis contains two functionally equivalent nuclei that are inherited independently during mitosis. Although presumed to be asexual, Giardia has low levels of allelic heterozygosity, indicating that the two nuclear genomes may exchange genetic material. Fluorescence in situ hybridization performed with probes to an episomal plasmid suggests that plasmids are transferred between nuclei in the cyst, and transmission electron micrographs demonstrate fusion between cyst nuclei. Green fluorescent protein fusions of giardial homologs of meiosis-specific genes localized to the nuclei of cysts, but not the vegetative trophozoite. These data suggest that the fusion of nuclei, or karyogamy, and subsequently somatic homologous recombination facilitated by the meiosis gene homologs, occur in the giardial cyst.     

植物自交不亲和性的分子生物学进展

自交不亲和性是植物特异性地识别并拒绝白花或亲缘关系很近的花粉的一种遗传机制,该特异性受S基因座控制。S-RNase介导的配子体型自交不亲和性在被子植物中分布最广泛,在茄科、蔷薇科和玄参科植物上研究比较深入。研究表明,雌雄双方的特异性决定因子分别是S基因座中具有多态性的核酸酶和含有F-box结构域蛋白基因,但其他修饰基因也参与其中。本文概括了该类自交不亲和性的研究现状,并根据最新研究进展就其工作模型作进一步探讨,同时简要提出今后的研究方向。     

The draft genome of Ciona intestinalis: insights into chordate and vertebrate origins

The first chordates appear in the fossil record at the time of the Cambrian explosion, nearly 550 million years ago. The modern ascidian tadpole represents a plausible approximation to these ancestral chordates. To illuminate the origins of chordate and vertebrates, we generated a draft of the protein-coding portion of the genome of the most studied ascidian, Ciona intestinalis. The Ciona genome contains approximately 16,000 protein-coding genes, similar to the number in other invertebrates, but only half that found in vertebrates. Vertebrate gene families are typically found in simplified form in Ciona, suggesting that ascidians contain the basic ancestral complement of genes involved in cell signaling and development. The ascidian genome has also acquired a number of lineage-specific innovations, including a group of genes engaged in cellulose metabolism that are related to those in bacteria and fungi.     

Systemic acquired resistance,NPR1, and pathogenesis-related genes in wheat and barley

In Arabidopsis, systemic acquired resistance (SAR) is established beyond the initial infection by a pathogen or is directly induced by treatment with salicylic acid (SA) or its functional analogs, 2,6-dichloroisonicotinic acid (INA) and benzothiadiazole (BTH). NPR1 protein is considered the master regulator of SAR in both SA signal sensing and transduction. In wheat (Triticum aestivum) and barley (Hordeum vulgare), both pathogen infection and BTH treatment can induce broad-spectrum resistance to various diseases, including powdery mildew, leaf rust, Fusarium head blight, etc. However, three different types of SAR-like responses including acquired resistance (AR), systemic immunity (SI), and BTH-induced resistance (BIR) seem to be achieved by activating different gene pathways. Recent research on wheat and barley NPR1 homologs in AR and SI has provided the initial clue for understanding the mechanism of SAR in these two plant species. In this review, the specific features of AR, SI, and BIR in wheat and barley were summarized and compared with that of SAR in model plants of Arabidopsis and rice. Research updates on downstream genes of SAR, including pathogenesis-related (PR) and BTH-induced genes, were highlighted.     

用18SrRNA序列探讨8种绿藻分子系统发育

测定了宽礁膜Monostroma latissimum、浒苔Enteromorpha prolifera、孔石莼Ulvapertusa的18SrRNA基因序列,并与肠浒苔Eintestinalis、穿孔石莼U.fenesrtata、石莼U.lactuca、礁膜M.nitidum和格氏礁膜Mottostroma grevillei5种已知的大型海洋绿藻的同一基因序列合并进行比较,分析了核苷酸序列差异和碱基替换特点,并构建系统发生树。结果表明：浒苔与肠浒苔之间的Kimura双参数距离大于浒苔与石莼属3个物种之间的Kimura双参数距离;用UPGMA法和MP法构建的系统树基本一致,在构建的系统发生树中,浒苔与石莼属物种聚为一类,表现出与石莼属物种更近的亲缘关系。     

Signaling the arrest of pollen tube development in self-incompatible plants

Self-incompatibility (SI), the cellular recognition system that limits inbreeding, has served as a paradigm for the study of cell-to-cell communication in plants since the phenomenon was first described by Darwin. Recent studies indicate that SI is achieved by diverse molecular mechanisms in different plant species. In the mustard family, the mechanism of SI shows parallels to the signaling systems found in animals that are mediated by cell-surface receptors with signal-transducing protein kinase activity.     

Genes of the major histocompatibility complex in mouse and man

The genes of the major histocompatibility complex code for cell-surface molecules that play an important role in the generation of the immune response. These genes and molecules have been studied intensively over the last five decades by geneticists, biochemists, and immunologists, but only recently has the isolation of the genes by molecular biologists facilitated their precise characterization. Many surprising findings have been made concerning their structure, multiplicity, organization, function, and evolution.     

Mcl-1 is essential for germinal center formation and B cell memory

Lymphocyte survival during immune responses is controlled by the relative expression of pro- and anti-apoptotic molecules, regulating the magnitude, quality, and duration of the response. We investigated the consequences of deleting genes encoding the anti-apoptotic molecules Mcl1 and Bcl2l1 (Bcl-x(L)) from B cells using an inducible system synchronized with expression of activation-induced cytidine deaminase (Aicda) after immunization. This revealed Mcl1 and not Bcl2l1 to be indispensable for the formation and persistence of germinal centers (GCs). Limiting Mcl1 expression reduced the magnitude of the GC response with an equivalent, but not greater, effect on memory B cell formation and no effect on persistence. Our results identify Mcl1 as the main anti-apoptotic regulator of activated B cell survival and suggest distinct mechanisms controlling survival of GC and memory B cells.     

海鞘(Ciona intestinalis)新microRNA基因的识别及其靶标预测

microRNAs(miRNAs)是一类长度约22 nt的非编码小RNA,通过碱基互补配对的方式调控靶基因的表达.本文采用同源搜索的方法,以线虫、果蝇、文昌鱼和人类的miRNA为探针,与海鞘的基因组序列进行比对,同时结合miRNA二级结构特征及SVM假阳性分析共发现10个新的miRNA基因.通过靶基因预测,共找出225个潜在靶基因,这些靶基因主要参与细胞代谢、转录调节、结合活性等功能.新miRNA基因的识别为海鞘miRNA功能研究奠定了基础,并为更进一步揭示脊椎动物miRNA的起源与进化提供了理论依据.     

Class II MHC molecules are specific receptors for staphylococcus enterotoxin A

T cell proliferation in response to stimulation with Staphylococcus enterotoxin A (SEA) requires accessory cells that express class II major histocompatibility complex (MHC) molecules. Murine fibroblasts transfected with genes encoding the alpha and beta subunits of HLA-DR, DQ, or DP were used to show that the proliferative response of purified human T cells to SEA is dependent on class II molecules but is not restricted by the haplotype of the responder. Binding of fluoresceinated SEA to class II transfectants and precipitation of class II heterodimers with SEA-Sepharose show that the proliferative response is a result of SEA binding to class II molecules. The binding is specific for class II molecules and is independent of class II allotype or isotype. The ability of SEA to bind class II molecules may be a general characteristic of this class of antigens, now called "superantigens".     

玻璃海鞘的营养成分分析

[目的]分析测定了玻璃海鞘的营养成分,并对其营养价值进行了评价。[方法]采用常规方法测定了水分、脂肪、蛋白质、灰分、氨基酸、脂肪酸和矿物质含量。[结果]玻璃海鞘水分、脂肪、蛋白质和灰分分别为：93.08%、2.08%、1.99%和2.7%。共检测了16种氨基酸,其中甘氨酸含量最高,必需氨基酸占总氨基酸的比值为42.51%,必需氨基酸和非必需氨基酸的比值为73.94%。测定了玻璃海鞘中13种脂肪酸,其中饱和脂肪酸8种,单不饱和脂肪酸2种,多不饱和脂肪酸3种,多不饱和脂肪酸含量占脂肪酸总量的13.8%。玻璃海鞘中含有丰富的Fe、Zn、Mn、Cu、N i等微量元素,对重金属等有毒有害物质分析结果表明其均符合国家相关安全卫生标准。[结论]玻璃海鞘营养价值较高,具有较好的开发前景。     

A 3-hydroxypropionate/4-hydroxybutyrate autotrophic carbon dioxide assimilation pathway in Archaea

The assimilation of carbon dioxide (CO2) into organic material is quantitatively the most important biosynthetic process. We discovered that an autotrophic member of the archaeal order Sulfolobales, Metallosphaera sedula, fixed CO2 with acetyl-coenzyme A (acetyl-CoA)/propionyl-CoA carboxylase as the key carboxylating enzyme. In this system, one acetyl-CoA and two bicarbonate molecules were reductively converted via 3-hydroxypropionate to succinyl-CoA. This intermediate was reduced to 4-hydroxybutyrate and converted into two acetyl-CoA molecules via 4-hydroxybutyryl-CoA dehydratase. The key genes of this pathway were found not only in Metallosphaera but also in Sulfolobus, Archaeoglobus, and Cenarchaeum species. Moreover, the Global Ocean Sampling database contains half as many 4-hydroxybutyryl-CoA dehydratase sequences as compared with those found for another key photosynthetic CO2-fixing enzyme, ribulose-1,5-bisphosphate carboxylase-oxygenase. This indicates the importance of this enzyme in global carbon cycling.     

赤霉素对梨糖代谢及其关键酶基因表达的影响

为了研究赤霉素增强果实库强的机制,以‘翠冠’梨(Pyrus pyrifolia Nakai)为试材,研究了赤霉素(GA)处理下果实膨大过程中果糖、葡萄糖、蔗糖、山梨糖醇和可溶性总糖含量变化及山梨糖醇和蔗糖代谢关键酶基因转录水平的影响。结果表明,6-磷酸山梨糖醇脱氢酶基因(S6PDH)表达量前期较低,随着果实膨大逐渐升高,并且GA促进S6PDH在果实膨大中后期的表达;山梨糖醇代谢关键酶NAD-山梨糖醇脱氢酶基因(NAD-SDH)在果实膨大前期相对表达量很高,GA抑制了果实膨大前期NAD-SDH的表达。在蔗糖代谢中,酸性转化酶基因(SI)的表达量随着果实的膨大逐渐上升,在膨大中期达到高峰,然后开始下降,且果肉中SI表达量较果芯中的高,GA显著促进果实膨大期果实中SI的表达。果芯中蔗糖磷酸合成酶基因(SPS)表达量随着果实成熟而持续增加,果芯中表达水平较高于果肉中,GA显著提高果实膨大中后期SPS的表达水平。蔗糖合成酶基因(SS)在果实膨大前期和中期表达水平较高,GA处理抑制SS表达。GA处理显著提高梨果肉和果芯组织中的可溶性糖含量,GA诱导糖代谢相关酶的基因的表达,并在果芯和果肉中存在空间表达差异。