贝西滑刃线虫糖苷水解酶16基因克隆及功能

为研究线虫寄生相关基因,基于贝西滑刃线虫转录组高通量测序数据,筛选并克隆了贝西滑刃线虫糖苷水解酶16基因,对该基因进行了功能分析;应用Mega 5.05选用WAG模型所构建的最大似然树进行分析比对;通过原位杂交,定位了糖苷水解酶16基因在线虫体内的表达部位,分析了糖苷水解酶蛋白的三维空间结构。结果表明:贝西滑刃线虫糖苷水解酶16基因与真菌亲缘关系近,是通过基因平移解说的一个重要佐证。

A Nucleus-encoded Topological Specificity Factor PpMinE in Physcomitrella patens has Conserved Function Similar to Its Chloroplast-encoded Ancestor

A nucleus-encoded MinE gene, designated PpMinE, from Physcomitrella patens was identified using RT-PCR. The presence of both N- and C-terminal extensions in PpMinE protein suggested its cyanobacterial origin. The transient expression of PpMinE using green fluorescent protein fusion in tobacco （Nicotiana tabacum L.） indicated that the PpMinE was a chloroplast-targeted protein. Overexpression of PpMinE in Escherichia coli caused division site misplacement and minicell formation, suggesting evolutionary functional conservation of MinE during plant phylogenesis. According to the phylogenetic tree, PpMinE protein has a close relationship with the highland plants, which suggests that the transfer events of MinE gene from plastid to nucleus might have occurred before the origin of the land plants.

A Minireview of Marine Algal Virus-Coccolithoviruses

Coccolithophorid is unicellular marine microalgae with a global distribution in temperate and sub-temperate oceanic regions and has the ability to produce ＇the coccoliths＇. It is considered to be the second most productive calcifying organism on earth and becoming an important factor in the global carbonate cycle. Emiliania huxleyi is one of the only two bloom-forming coccolithophores and becomes a species crucial to the study of global biogeochemical cycles and climate modeling. Coccolithoviruse is a recently discovered group of viruses infecting the marine coceolithophorid E. huxleyi. They are a major cause of coceolithophore bloom termination, and DMSP concentration is increasing in the process of viral lysis. Phylogenetic evidences support that some genes are functional both in E. huxleyi and its virus （EhV）. Horizontal gene transfer （HGT） of multiple functionally coupled enzymes occurs in E. huxleyi and its DNA virus EhV has been confirmed, which contributes to the diversification and adaptation of plankton in the oceans and also critically regulates virus-host infection by allowing viruses to control host metabolic pathways for their repli- cation. Therefore, it is of particular interest to understand this host-virus interaction. On this issue, we have made a minireview of coeeolithoviruses focusing on the basic characteristics, phylogenesis, horizontal gene transfer and the interaction between the host and its viruses, as well as its important role in global biogeochemical cycling.

Adenovirus-mediated gene transfer of TIMP-4 reduces neointimal hyperplasia in balloon-injured rat carotid artery

Objective:To determine the effects of a recombinant replication-deficient adenovirus encoding human tissue inhibitor of metalloproteinase-4(Ad.TIMP-4) on vascular smooth muscle cell(VSMC) function in vitro and neointimal development in the injured rat carotid artery.Methods:Western blotting,gelatin zymography and reverse zymography were used to characterize the expression and functional activity of the TIMP-4 secreted by Ad.TIMP-4-infected VSMCs.The migration and proliferation of VSMCs in vitro were separately detected by using Millicell-PCF invasion chambers and [3H]-thymidine incorporation assay.Immunohistochemistry and morphometric analysis were used to determine the local expression of TIMP-4 and its effect on neointima development in a rat carotid artery balloon injury model.Results:VSMCs infected with Ad.TIMP-4 expressed functionally active human TIMP-4 which increased with the duration of infection.TIMP-4 expression inhibited VSMC migration,but not significantly affect VSMC proliferation.In a balloon-injured rat carotid artery model,a significant 62% reduction in neointimal area was found in Ad.TIMP-4-infected vessels at 14 days after injury.Ad.TIMP-4 infection had no effect on medial area.Conclusion:Our results indicated TIMP-4 over expression can significantly inhibit the migration of cultured VSMCs and prevent neointimal formation after vascular injury.Our findings provide additional evidence that TIMP-4 could play an important role in vascular pathophysiology,and may be an important therapeutic target for future drug development.

VERTICAL HEREDITY VS. HORIZONTAL GENE TRANSFER: A CHALLENGE TO BACTERIAL CLASSIFICATION

The diversity and classification of microbes has been a long-standing issue.Molecular phylogeny of the prokaryotes based on comparison of the 16S rRNA sequences of the small ribosomal subunit has led to a reasonable tree of life in the late 1970s. How-ever, the availability of more and more complete bacterial genomes has brought about complications instead of refinement of the tree. In particular, it turns out that different choice of genes may tell different history. This might be caused by possible horizontal gene transfer (HGT) among species. There is an urgent need to develop phylogenetic methods that make use of whole genome data. We describe a new approach in molecular phylogeny,namely, tree construction based on K-tuple frequency analysis of the genomic sequences.Putting aside the technicalities, we emphasize the transition from randomness to determin-ism when the string length K increases and try to comment on the challenge mentioned in the title.

A monocot-specific hydroxycinnamoylputrescine gene cluster contributes to immunity and cell death in rice

Phenolamides(PAs), a diverse group of specialized metabolites, including hydroxycinnamoylputrescine(HP), hydroxycinnamoylagmatine, and hydroxycinnamoyltryptamine, are important in plant resistance to biotic stress. However, the genes involved in the biosynthesis and modulation of PAs have not been fully elucidated. This study identified an HP biosynthetic gene cluster in rice(Oryza sativa) comprising one gene(Os ODC) encoding a decarboxylase and two tandem-duplicated genes(Os PHT3 and Os PHT4)encoding putrescine hydroxycinnamoyl acyltransferases coexpressed in different tissues. Os ODC catalyzes the conversion of ornithine to putrescine, which is used in HP biosynthesis involving Os PHT3 and Os PHT4. Os PHT3 or Os PHT4 overexpression causes HP accumulation and cell death and putrescine hydroxycinnamoyl acyltransferases(PHT) activity-dependent resistance against the fungal pathogen Magnaporthe oryzae. Os ODC overexpression plants also confer enhanced resistance to M. oryzae.Notably, the basic leucine zipper transcription factor APIP5, a negative regulator of cell death, directly binds to the Os PHT4 promoter, repressing its transcription. Moreover, APIP5 suppression induces Os PHT4 expression and HP accumulation. Comparative genomic analysis revealed that the HP biosynthetic gene cluster is conserved in monocots. These results characterized a previously unidentified monocot-specific gene cluster that is involved in HP biosynthesis and contributes to defense and cell death in rice.