Hawaiian Drosophila offer an excellent model for adaptive evolution. More than 500 species are reported in Hawaiian islands, and there is considerable diversity in behavior and morphology. Such diversity is mainly driven by sexual selection. In this study qualitative and quantitative chemical compositions of cuticular hydrocarbons (CHCs) in 138 flies belonging to 27 Hawaiian Drosophila species, picture-winged and non picture-winged, were analyzed regarding sexual dimorphism, differences in saturation, branching position, and lengths of CHCs. We found significant variation in the CHC patterns. In several subgroups, new species show decreases in unsaturated hydrocarbons, and gradual increases in branched compounds, monomethylalkanes and dimethylalkanes, not commonly found in Drosophila. Moreover, branching positions gradually shifted towards internal carbons, and chain lengths increased in the new species. The long-term evolution of CHCs in the light of the recent evolutionary migration and adaptation history of Hawaiian Drosophila species along the developing archipelago was discussed.

Leptin, a polypeptide hormone secreted mainly by adipose tissue, plays an important role in feed intake regulation, energy metabolism and reproduction in several species. Its function has been intensively studied in mammals; however, in birds limited information is available. The cDNA sequence for chicken leptin has been reported, and high hepatic expression levels of leptin were associated with fat deposition in selected bird lines. However, controversies still remain concerning to the chicken leptin gene and several authors failed to amplify this gene from genomic DNA or cDNA. In view of this controversy and the importance of this gene, the present study aimed to investigate the leptin gene in a population of birds developed by Embrapa Swine and Poultry Research Center (Brazil). First of all, the sequences of Gallus gallus leptin gene (GenBank AF012727) and Mus musculus (GenBank NM_008493) were aligned with the objective of designing primers in conserved regions among the two species, since 94.6% of similarity is described in the literature in those species. For all four pairs of primers designed, several amplification tests were performed with both DNA and cDNA, but neither unique fragment nor expected band size was ever achieved. The leptin sequence in GenBank does not represent the sequence of the chicken leptin gene.

Chicken Expressed Sequence Tags (ESTs) were analyzed to identify genes associated with myogenesis during embryonic development. A total of 6,184 ESTs were generated from three cDNA libraries constructed from whole embryos (Stage 26), somites associated with neural tube (Stage 15), and limb buds (Stages 21, 24 and 26). Clustering and assembly of 4,998 valid ESTs resulted in 2,329 unique sequences with 902 clusters (38.7%) and 1,427 singletons (61.3%). There are more than 400,000 chicken ESTs available at GenBank and we were able to identify 143 novel sequences. From these, 45 sequences found either a human EST homolog or a match with conserved regions among proteins. Most of these sequences were found to be expressed in somites, an important tissue for muscle development and not characterized before. This study revealed the value of micro dissected embryonic libraries for describing gene expression profiles associated with myogenesis and gene discovery.

Important advances have been made in understanding the genetic processes that control skeletal muscle formation. Studies conducted on quails detected a delay in the myogenic program of animals selected for high growth rates. These studies have led to the hypothesis that a delay in myogenesis would allow somitic cells to proliferate longer and consequently increase the number of embryonic myoblasts. To test this hypothesis, recently segmented somites and part of the unsegmented paraxial mesoderm were separated from the neural tube/ notochord complex in HH12 chicken embryos. In situ hybridization and competitive RT-PCR revealed that MyoD transcripts, which are responsible for myoblast determination, were absent in somites separated from neural tube/notochord (1.06 and 0.06 10 -3 attomol MyoD/ 1 attomol ß-actin for control and separated somites, respectively; P<0.01). However, reapproximation of these structures allowed MyoD to be expressed in somites. Cellular proliferation was analyzed by immunohistochemical detection of incorporated BrdU, a thymidine analogue. A smaller but not significant (P = 0.27) number of proliferating cells was observed in somites that had been separated from neural tube/notochord (27 and 18 for control and separated somites, respectively). These results confirm the influence of the axial structures on MyoD activation but do not support the hypothesis that in the absence of MyoD transcripts the cellular proliferation would be maintained for a longer period of time.

In situ hybridization has provided insights into the molecular basis of skeletal myogenesis during embryonic development. In situ detection of different muscle-specific regulatory factors in whole embryos has been described. Spatial and temporal expression patterns of these factors differed among species. The expression pattern of MyoD in whole chicken embryos was studied via in situ hybridization using a probe obtained by the reverse transcription - polymerase chain reaction (RT-PCR) technique. In newly formed somites (embryos of stage 12), MyoD mRNA transcripts were detected along the anterior to posterior axis of somites immediately adjacent to the neural tube, whereas in mature somites (embryos of stage 24), MyoD transcripts were detected throughout the entire somite. These results indicate that MyoD expression is important for initiating and maintaining the avian myogenic system.

, agradeço pela oportunidade, orientação e pelos valiosos ensinamentos. À FAPESP pelo apoio financeiro ao desenvolvimento deste trabalho. Aos professores do Departamento de Produção Animal pelos ensinamentos adquiridos. Às secretárias do Departamento de Produção Animal pelo atendimento e atenção recebidos. Ao funcionário Alexandre do Departamento de Produção Animal, pela ajuda nos experimentos. Ao Dr. André Vettore, Dra. Otavia Caballero e à Márcia pela ajuda recebida. À Dra. Cláudia Barros Monteiro Vitorello pela grande ajuda, apoio e amizade. Ao Centro Nacional de Pesquisa de Suínos e Aves (CNPSA-EMBRAPA) pela valiosa colaboração. À Dra. Mônica Correa Ledur pelo apoio e amizade. Ao amigo Marcelo de Lima Marchesin pela valiosa ajuda em todas as etapas deste trabalho. Às amigas Érika, Clarissa, Rachel e Gisele pela ajuda na realização deste trabalho. Aos meus pais e irmãos, pelo carinho, incentivo e apoio sempre recebidos. Ao Junior, pelo apoio, carinho e incentivo em todos os momentos. Ao pessoal do Laboratório de Biotecnologia pela amizade e convivência. À todos aqueles que de alguma maneira contribuíram para a realização deste trabalho.

Brazilian poultry industry has reached a high level of development in both meat and egg production as a result of constant technological modernization. Further improvements can be achieved through genomics, but before this can be accomplished, a better understanding of gene expression profiles and nucleotide polymorphisms is necessary. Since animal physiology is directly or indirectly controlled by the pituitary and hypothalamus, the aim of the present work was to identify and analyze genes expressed in these tissues in chicken lines with different growth potential. Two pituitary and hypothalamus cDNA libraries from 21 day broiler (TT) and layer (CC) chickens lines were constructed and allowed identification of 3,074 unique sequences and 77 single nucleotide polymorphisms (SNPs). The collection of expressed sequence tags (ESTs) and SNPs identified in this study represents an important resource for future studies aimed at identifying genes responsible for growth in chicken.

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