RESUMO
Sequencing of multiple related species followed by comparative genomics analysis constitutes a powerful approach for the systematic understanding of any genome. Here, we use the genomes of 12 Drosophila species for the de novo discovery of functional elements in the fly. Each type of functional element shows characteristic patterns of change, or 'evolutionary signatures', dictated by its precise selective constraints. Such signatures enable recognition of new protein-coding genes and exons, spurious and incorrect gene annotations, and numerous unusual gene structures, including abundant stop-codon readthrough. Similarly, we predict non-protein-coding RNA genes and structures, and new microRNA (miRNA) genes. We provide evidence of miRNA processing and functionality from both hairpin arms and both DNA strands. We identify several classes of pre- and post-transcriptional regulatory motifs, and predict individual motif instances with high confidence. We also study how discovery power scales with the divergence and number of species compared, and we provide general guidelines for comparative studies.
Assuntos
Drosophila/classificação , Drosophila/genética , Evolução Molecular , Genoma de Inseto/genética , Genômica , Animais , Sequência de Bases , Sítios de Ligação , Sequência Conservada , Proteínas de Drosophila/genética , Éxons/genética , Regulação da Expressão Gênica/genética , Genes de Insetos/genética , MicroRNAs/genética , Dados de Sequência Molecular , Especificidade de Órgãos , Filogenia , Regiões não Traduzidas/genéticaRESUMO
The Notch signaling pathway plays an important role during development in animals from worms to humans and pathway components are required for the differentiation of many different cell types. In Drosophila, Su(H) dependent Notch activation up-regulates transcription of the Enhancer of split-Complex (E(spl)-C). The E(spl) genes are known to function during neurogenesis, although expression and genetics studies suggest that they also play roles in the development of other tissues. The majority of the E(spl) genes contain upstream binding sites for Su(H), proneural proteins, and E(spl) bHLH proteins resulting in overlapping expression patterns during embryonic development. However, their expression patterns are quite distinct during later embryonic stages and in larval imaginal discs. In order to characterize expression patterns of the E(spl) genes during development and determine potential mechanisms through which expression is controlled, we examined the expression levels and patterns of the E(spl) genes in the midgut during metamorphosis. Quantitative Reverse Transcriptase-PCR and X-Gal staining results show that the genes have different levels and patterns of expression in the developing midgut. Two ancestral E(spl) genes, malpha and mbeta, are highly expressed and increase significantly at puparium formation, whereas another gene, mgamma, is expressed at low levels and decreases in expression at puparium formation. We also show that mbeta is expressed in cells throughout the midgut, while mgamma is expressed in two small regions. These results provide further evidence that the E(spl) genes function during midgut development and that they are regulated by different factors.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Proteínas de Drosophila/genética , Drosophila/genética , Regulação da Expressão Gênica no Desenvolvimento , Proteínas Repressoras/genética , Animais , Drosophila/crescimento & desenvolvimento , Genes de Insetos , Intestinos/crescimento & desenvolvimento , Receptores Notch/genéticaRESUMO
During Drosophila development Suppressor of Hairless [Su(H)]-dependent Notch activation upregulates transcription of the Enhancer of split-Complex [E(spl)-C] genes. Drosophila melanogaster E(spl) genes share common transcription regulators including binding sites for Su(H), proneural, and E(spl) basic-helix-loop-helix (bHLH) proteins. However, the expression patterns of E(spl) genes during development suggest that additional factors are involved. To better understand regulators responsible for these expression patterns, recently available sequence and annotation data for multiple Drosophila genomes were used to compare the E(spl) upstream regulatory regions from more than nine Drosophila species. The mgamma and mbeta regulatory regions are the most conserved of the bHLH genes. Fine analysis of Su(H) sites showed that high-affinity Su(H) paired sites and the Su(H) paired site plus proneural site (SPS + A) architecture are completely conserved in a subset of Drosophila E(spl) genes. The SPS + A module is also present in the upstream regulatory regions of the more ancient mosquito and honeybee E(spl) bHLH genes. Additional transcription factor binding sites were identified upstream of the E(spl) genes and compared between species of Drosophila. Conserved sites provide new understandings about E(spl) regulation during development. Conserved novel sequences found upstream of multiple E(spl) genes may play a role in the expression of these genes.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Proteínas de Drosophila/genética , Drosophila/genética , Genes de Insetos , Proteínas Repressoras/genética , Animais , Anopheles/genética , Sequência de Bases , Abelhas/genética , Sítios de Ligação/genética , Sequência Conservada , DNA/genética , DNA/metabolismo , Pegada de DNA , Drosophila/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Evolução Molecular , Genes Reguladores , Dados de Sequência Molecular , Filogenia , Regiões Promotoras Genéticas , Especificidade da Espécie , Fatores de Transcrição/metabolismoRESUMO
Many initiatives for the improvement of undergraduate science education call for inquiry-based learning that emphasizes investigative projects and reading of the primary literature. These approaches give students an understanding of science as a process and help them integrate content presented in courses. At the same time, general initiatives to promote information fluency are being promoted on many college and university campuses. Information fluency refers to discipline-specific processing of information, and it involves integration of gathered information with specific ideas to form logical conclusions. We have implemented the use of inquiry-based learning to enhance and study discipline-specific information fluency skills in an upper-level undergraduate Developmental Biology course. In this study, an information literacy tutorial and a set of linked assignments using primary literature analysis were integrated with two inquiry-based laboratory research projects. Quantitative analysis of student responses suggests that the abilities of students to identify and apply valid sources of information were enhanced. Qualitative assessment revealed a set of patterns by which students gather and apply information. Self-assessment responses indicated that students recognized the impact of the assignments on their abilities to gather and apply information and that they were more confident about these abilities for future biology courses and beyond.