Transpositional behaviour of the Ds element in the Ac/Ds system in rice

Insertional mutagenesis based on maize Activator/Dissociator (Ac/Ds) transposons is becoming a ma- jor approach used to produce a saturated mutant collection in rice. In this research, Ds-T-DNA trans- formed homozygotes were crossed with Ac-T-DNA transformed homozygotes in order to establish an Ac/Ds transposon system in rice. The successive investigation of Ds transposition from F1 to F5 gen- erations indicated that the frequencies of germinal transposition increased over successive genera- tions and reached 54.2% in F3 generation. The Ds transposition pattern revealed that a Ds transposition induced an approximately 170-bp deletion of T-DNA sequence and another Ds transposition carried a 272-bp T-DNA sequence. Using thermal asymmetric interlaced PCR (TAIL-PCR), some flanking se- quences of the Ds element were amplified. Analyses of 17 Ds-flanking sequences showed that five Ds were inserted into gene regions. The Ds could transpose not only to the linked sites but also to the unlinked sites. The frequency of inter-chromosomal transposition of Ds was 33.3%.     

Isolation ofosRACD gene encoding a small GTP-binding protein from rice

Using an improved version of mRNA differential display technology, we have obtained a differentially displayed fragment RDP-8. Homologous comparison indicated that the fragment RDP-8 has high homology with the gene encoding maize small GTP-binding protein. By screening cDNA library of the rice Nongken 58N pan icle using the newly obtained fragment RDP-8 as probe, we further found the full-length cDNA of osRACD gene that encodes a rice small GTP-binding protein. Asco mpared with maize RACD gene, the osRACD of rice shows remarkable homology in both nucleotide sequence and amino acid sequence, 88% and 97% respectively. Evidence from RT-PCR study indicates that osRACD gene is related to photoperiod fertility conversion of photoperiod sensitive genic male sterility (PSGMS) rice.     

玉米淀粉合成相关基因ZmSSIIa 的序列变异分析

 玉米淀粉合成酶ZmSSIIa 在淀粉生物合成途径中主要作用是将支链淀粉的分支链由6~10 个延长至12~25 个, 对于玉米籽粒产量和品质具有重要的影响。本研究在86 个优异玉米自交系中对该基因进行基因序列定点捕获, 并获得该基因全长为4836 bp 的核苷酸序列。基因多态性分析发现, 该基因座位上有78 个SNP 和19 个Indel。玉米ZmSSIIa 基因的编码区具有24个SNP, 将该基因划分成9 种编码区单倍型, 并编码7 种ZmSSIIa 蛋白质。供试材料的群体中, ZmSSIIa 基因至少经历8 次重组, 可能对单倍型的分化和连锁不平衡具有重要作用。中性进化测试表明该基因在供试群体中没有明显的人工选择。     

植物转座元件及其表观遗传调控?

植物的转座元件对于植物基因组的组成、进化和基因表达都具有重要影响.植物绝大部分的转座元件都处于沉默状态.植物机体通过一套识别转座元件并进行表观遗传沉默的有效机制,可逆地调控着转座元件的激活与沉默.本文综述了转座元件沉默和激活的表观遗传机制.     

Mobilization of a Drosophila transposon in the Caenorhabditis elegans germ line.

Transposons have been enormously useful for genetic analysis in both Drosophila and bacteria. Mutagenic insertions constitute molecular tags that are used to rapidly clone the mutated gene. Such techniques would be especially advantageous in the nematode Caenorhabditis elegans, as the entire sequence of the genome has been determined. Several different types of endogenous transposons are present in C. elegans, and these can be mobilized in mutator strains (reviewed in ref. 1). Unfortunately, use of these native transposons for regulated transposition in C. elegans is limited. First, all strains contain multiple copies of these transposons and thus new insertions do not provide unique tags. Second, mutator strains tend to activate the transposition of several classes of transposons, so that the type of transposon associated with a particular mutation is not known. Here we demonstrate that the Drosophila mariner element Mos1 can be mobilized in C. elegans. First, efficient mobilization of Mos1 is possible in somatic cells. Second, heritable insertions of the transposon can be generated in the germ line. Third, genes that have been mutated by insertion can be rapidly identified using inverse polymerase chain reaction. Fourth, these insertions can subsequently be remobilized to generate deletion and frameshift mutations by imperfect excision.     

转座子的起源及其和物种进化的关系

关于转座子的属性及其起源问题现在还没有解决,在这篇论文中,作者经过分析提出了转座子由病毒或逆转录病毒退化而来的观点,并且阐述了转座子与物种进化之间的关系,主要从转座子影响物种适应性和引起基因突变,染色体畸变两个方面进行了说明。     

Genome of the marsupial Monodelphis domestica reveals innovation in non-coding sequences

We report a high-quality draft of the genome sequence of the grey, short-tailed opossum (Monodelphis domestica). As the first metatherian ('marsupial') species to be sequenced, the opossum provides a unique perspective on the organization and evolution of mammalian genomes. Distinctive features of the opossum chromosomes provide support for recent theories about genome evolution and function, including a strong influence of biased gene conversion on nucleotide sequence composition, and a relationship between chromosomal characteristics and X chromosome inactivation. Comparison of opossum and eutherian genomes also reveals a sharp difference in evolutionary innovation between protein-coding and non-coding functional elements. True innovation in protein-coding genes seems to be relatively rare, with lineage-specific differences being largely due to diversification and rapid turnover in gene families involved in environmental interactions. In contrast, about 20% of eutherian conserved non-coding elements (CNEs) are recent inventions that postdate the divergence of Eutheria and Metatheria. A substantial proportion of these eutherian-specific CNEs arose from sequence inserted by transposable elements, pointing to transposons as a major creative force in the evolution of mammalian gene regulation.     

Identification of the Angel -related elements in cyprinid fishes and their phylogenetic implications

Angel-related element belongs to the family of miniature inverted-repeat transposable elements (MITEs). In this paper we report the identification of an Angel- related element in the series Leuciscini of cyprinid fishes, which is located in the second intron of the growth hormone (GH) gene. We have also found that this element is absent in orthologous locus in the series Barbini of cyprinid fishes, that provides new evidence for the monophyly of the series Leuciscini. The insertion of Angel -related element into the GH gene might take place in the common ancestor of the series Leuciscini after its divergence from the series Barbini. The high sequence divergence and relatively broad species distribution of Angel-related elements implies that they might be ancient transposons which appeared about 26 million years ago.     

Identification of the Angel-related elements in cyprinid fishes and their phylogenetic implications

Angel-related element belongs to the family of miniature inverted-repeat transposable elements (MITEs). In this paper we report the identification of an Angel-related element in the series Leuciscini of cyprinid fishes, which is located in the second intron of the growth hormone (GH) gene. We have also found that this element is absent in orthologous locus in the series Barbini of cyprinid fishes, that provides new evidence for the monophyly of the series Leuciscini. The insertion of Angel-related element into the GH gene might take place in the common ancestor of the series Leuciscini after its divergence from the series Barbini. The high sequence divergence and relatively broad species distribution of Angel-related elements implies that they might be ancient transposons which appeared about 26 million years ago.     

Genome-wide non-mendelian inheritance of extra-genomic information in Arabidopsis

A fundamental tenet of classical mendelian genetics is that allelic information is stably inherited from one generation to the next, resulting in predictable segregation patterns of differing alleles. Although several exceptions to this principle are known, all represent specialized cases that are mechanistically restricted to either a limited set of specific genes (for example mating type conversion in yeast) or specific types of alleles (for example alleles containing transposons or repeated sequences). Here we show that Arabidopsis plants homozygous for recessive mutant alleles of the organ fusion gene HOTHEAD (HTH) can inherit allele-specific DNA sequence information that was not present in the chromosomal genome of their parents but was present in previous generations. This previously undescribed process is shown to occur at all DNA sequence polymorphisms examined and therefore seems to be a general mechanism for extra-genomic inheritance of DNA sequence information. We postulate that these genetic restoration events are the result of a template-directed process that makes use of an ancestral RNA-sequence cache.     

玉米ELM1基因的序列变异及与株型和穗部相关性状的关联分析

 玉米elm1 突变体使得光敏色素载色体合成受阻并导致光敏色素活性下降,从而使得突变体植株表现出对光的不敏感性.为研究玉米ELM1 基因序列的多态性及其与主要农艺性状之间的关联,本研究对玉米ELM1 基因在80 个自交系中进行了目标序列重测序,并与株高和穗位高2 个株型性状以及穗长、穗粗、轴粗、穗重、行粒数、穗行数和穗粒数7 个穗部性状进行关联分析.ELM1 基因在供试玉米自交系中共有85 个变异,包括73 个SNP 和12 个Indel.尽管该基因的编码区不含Indel,但15 个SNP 变异位点依然可以将编码区划分成7 种单倍型,并编码6 种ELM1 蛋白质.关联分析发现,玉米ELM1 基因中1 个非同义突变位点与穗位高存在显著关联,另有2 个非同义突变位点与行粒数存在显著关联.     

水稻白叶枯病菌1个毒性相关基因的鉴定

我们曾报道了来自水稻白叶枯病菌真基文库的重级质粒ｐＧＸＮ３０００中含有一个能互补甘蓝黑腐病菌ｒｐｆＧ致病因子调控基因突变全的基因，并通过转座子诱变获得子转座子插在ｐＧＸＮ３０００中的这一基因的转座子插重组质粒，本研究利用这些转座子插入重组质粒，通过标记置换方法构建了不稻白叶枯病菌这一基因的突变菌株，植株试验结果表明，突变株虽然在水稻中仍能正常生长繁殖，但毒性严重降低，说明水稻白叶枯病菌的这一基因在     

水稻苹果酸脱氢酶基因的克隆及其在E.coli中的表达

以玉米苹果酸脱氢酶的基因为探针，从水稻幼苗cDNA文库筛选得到一条水稻新基因，它与玉米ZHO2序列的一致性高达87％，被命名为RcMDH(rice cytoplasmic malic dehydrogenase gene)，分析发现RcMDH具有完整的读码框，编码332个氨基酸，预计分子质量为36．5ku,导入大肠杆菌中表达，经检测证实该产物具苹果酸脱氢酶酶活性。     

DNA sequence of the maize transposable element Dissociation

The DNA sequence of the terminal 4.2 kilobases (kb) of the 30-kb insertion in the endosperm sucrose synthase gene of maize mutant sh-m5933 shows that it comprises two identical 2,040-base pair (bp) segments, one inserted in the reverse direction into the other. We suggest that the 2,040-bp sequence is an example of the transposable element Dissociation described by Barbara McClintock.     

A genetic link between co-suppression and RNA interference in C. elegans

Originally discovered in plants, the phenomenon of co-suppression by transgenic DNA has since been observed in many organisms from fungi to animals: introduction of transgenic copies of a gene results in reduced expression of the transgene as well as the endogenous gene. The effect depends on sequence identity between transgene and endogenous gene. Some cases of co-suppression resemble RNA interference (the experimental silencing of genes by the introduction of double-stranded RNA), as RNA seems to be both an important initiator and a target in these processes. Here we show that co-suppression in Caenorhabditis elegans is also probably mediated by RNA molecules. Both RNA interference and co-suppression have been implicated in the silencing of transposons. We now report that mutants of C. elegans that are defective in transposon silencing and RNA interference (mut-2, mut-7, mut-8 and mut-9) are in addition resistant to co-suppression. This indicates that RNA interference and co-suppression in C. elegans may be mediated at least in part by the same molecular machinery, possibly through RNA-guided degradation of messenger RNA molecules.     

玉米矮花叶病毒外壳蛋白基因的克隆研究

玉米(Zea mays L.)矮花叶病在国内外广泛发生,且在玉米生产中造成了重大损失.通过RT-PCR法从具有典型的玉米矮花叶病症状的玉米叶片中克隆了外壳蛋白(Coat protein,CP)基因,测序和同源性比较表明所克隆的CP基因来自玉米矮花叶病毒(Maize dwarf mosaic virus,MDMV)B株系,全长920个碱基对,开放阅读框编码219个氨基酸,该基因可进一步用于玉米抗矮花叶病的转基因研究,以获得生产应用的抗病材料.     

玉米抗旱性的研究进展(综述)

玉米的抗旱机理十分复杂,其中适应干旱的形态结构特征是玉米长期进化的结果,通过生理代谢调节也是玉米适应抗旱的有效手段之一.玉米抗旱性是由多基因控制,呈现典型的数量遗传.对玉米抗旱机理及其基因工程改良的最新进展作了系统的介绍,并探讨了今后玉米抗旱性研究发展方向.