Electron-Pair Theories of Molecular Electronic Structure

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Antiviral roles of plant ARGONAUTES

[EN] ARGONAUTES (AGOs) are the effector proteins functioning in eukaryotic RNA silencing pathways. AGOs associate with small RNAs and are programmed to target complementary RNA or DNA. Plant viruses induce a potent and specific antiviral RNA silencing host response in which AGOs play a central role. Antiviral AGOs associate with virus-derived small RNAs to repress complementary viral RNAs or DNAs, or with endogenous small RNAs to regulate host gene expression and promote antiviral defense. Here, we review recent progress towards understanding the roles of plant AGOs in antiviral defense. We also discuss the strategies that viruses have evolved to modulate, attenuate or suppress AGO antiviral functions.We thank members of the Carrington lab for useful and crucial discussions, and apologize to those colleagues whose work could not be cited because of space and reference limitations. This work was supported by grants from the National Science Foundation (MCB-1231726 and MCB-1330562) and National Institutes of Health (AI043288) to James C Carrington, and from the European Commission (H2020-MSCA-IF-2014-655841) to Alberto Carbonell.Carbonell, A.; Carrington, JC. (2015). Antiviral roles of plant ARGONAUTES. Current Opinion in Plant Biology. 27:111-117. https://doi.org/10.1016/j.pbi.2015.06.013S11111727Meister, G. (2013). Argonaute proteins: functional insights and emerging roles. Nature Reviews Genetics, 14(7), 447-459. doi:10.1038/nrg3462Poulsen, C., Vaucheret, H., & Brodersen, P. (2013). Lessons on RNA Silencing Mechanisms in Plants from Eukaryotic Argonaute Structures. The Plant Cell, 25(1), 22-37. doi:10.1105/tpc.112.105643Martínez de Alba, A. E., Elvira-Matelot, E., & Vaucheret, H. (2013). Gene silencing in plants: A diversity of pathways. 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Negative Attitudes of Law Students: A Replication of the Alienation and Dissatisfaction Factors

In 1976 we conducted a survey of law students at The University of Michigan. Demographic information; personal goals and values; and attitudes toward the law school, the faculty, and fellow students were surveyed. We factor-analyzed the items relating to attitudes, personal goals, and values. Three major factors were identified and labeled as alienation, dissatisfaction, and sociability. We have recently described the alienation factor extensively and outlined the dissatisfaction and sociability factors. In March 1977, we conducted a second survey designed to replicate the earlier study. Despite the addition of a few new items, the questionnaire was essentially unchanged. The new study group consisted of 165 first-year students and 38 second- or third-year students. We randomly selected the first-year students from the class entering in 1976. The advanced students were enrolled in a course on evidence. We used the same procedure as in the first study to factor-analyze the data. The first two rotated factors-alienation and dissatisfaction-were quite comparable to those in the earlier study. The third factor, sociability, did not replicate, and it seems advisable to discard it as a central construct in studies of the professional socialization of law students

Whole-genome analysis of animal A- and B-type cyclins.

BACKGROUND: Multiple A- and B-type cyclins have been identified in animals, but their study is complicated by varying degrees of functional redundancy. A non-essential phenotype may reflect redundancy with a known or as yet unknown gene. Complete sequencing of several animal genomes has allowed us to determine the size of the mitotic cyclin gene family and therefore to start to address this issue. RESULTS: We analyzed the Caenorhabditis elegans, Drosophila melanogaster and Homo sapiens genomes to identify known and novel A- and B-type cyclin genes and distinguish them from related pseudogenes. We find only a single functional A-type cyclin gene in invertebrates but two in vertebrates. In addition to the single functional cyclin A gene, the C. elegans genome contains numerous cyclin A pseudogenes. In contrast, the number and relationship of B-type cyclins varies considerably between organisms but all contain at least one cyclin B1-like gene and a cyclin B3 gene. CONCLUSIONS: There are three conserved families of mitotic cyclins in animals: A-, B3- and B-type. The precise number of genes within the A- and B-type families varies in different organisms, possibly as an adaptation to their distinct developmental strategies.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Whole-genome analysis of animal A- and B-type cyclins

BACKGROUND: Multiple A- and B-type cyclins have been identified in animals, but their study is complicated by varying degrees of functional redundancy. A non-essential phenotype may reflect redundancy with a known or as yet unknown gene. Complete sequencing of several animal genomes has allowed us to determine the size of the mitotic cyclin gene family and therefore to start to address this issue. RESULTS: We analyzed the Caenorhabditis elegans, Drosophila melanogaster and Homo sapiens genomes to identify known and novel A- and B-type cyclin genes and distinguish them from related pseudogenes. We find only a single functional A-type cyclin gene in invertebrates but two in vertebrates. In addition to the single functional cyclin A gene, the C. elegans genome contains numerous cyclin A pseudogenes. In contrast, the number and relationship of B-type cyclins varies considerably between organisms but all contain at least one cyclin B1-like gene and a cyclin B3 gene. CONCLUSIONS: There are three conserved families of mitotic cyclins in animals: A-, B3- and B-type. The precise number of genes within the A- and B-type families varies in different organisms, possibly as an adaptation to their distinct developmental strategies

Small RNA-based antiviral defense in the phytopathogenic fungus Colletotrichum higginsianum

Even though the fungal kingdom contains more than 3 million species, little is known about the biological roles of RNA silencing in fungi. The Colletotrichum genus comprises fungal species that are pathogenic for a wide range of crop species worldwide. To investigate the role of RNA silencing in the ascomycete fungus Colletotrichum higginsianum, knock-out mutants affecting genes for three RNA-dependent RNA polymerase (RDR), two Dicer-like (DCL), and two Argonaute (AGO) proteins were generated by targeted gene replacement. No effects were observed on vegetative growth for any mutant strain when grown on complex or minimal media. However, Δdcl1, Δdcl1Δdcl2 double mutant, and Δago1 strains showed severe defects in conidiation and conidia morphology. Total RNA transcripts and small RNA populations were analyzed in parental and mutant strains. The greatest effects on both RNA populations was observed in the Δdcl1, Δdcl1Δdcl2, and Δago1 strains, in which a previously uncharacterized dsRNA mycovirus [termed Colletotrichum higginsianum non-segmented dsRNA virus 1 (ChNRV1)] was derepressed. Phylogenetic analyses clearly showed a close relationship between ChNRV1 and members of the segmented Partitiviridae family, despite the non-segmented nature of the genome. Immunoprecipitation of small RNAs associated with AGO1 showed abundant loading of 5'U-containing viral siRNA. C. higginsianum parental and Δdcl1 mutant strains cured of ChNRV1 revealed that the conidiation and spore morphology defects were primarily caused by ChNRV1. Based on these results, RNA silencing involving ChDCL1 and ChAGO1 in C. higginsianum is proposed to function as an antiviral mechanism