Transcriptomic analyses of regenerating adult feathers in chicken.

BACKGROUND: Feathers have diverse forms with hierarchical branching patterns and are an excellent model for studying the development and evolution of morphological traits. The complex structure of feathers allows for various types of morphological changes to occur. The genetic basis of the structural differences between different parts of a feather and between different types of feather is a fundamental question in the study of feather diversity, yet there is only limited relevant information for gene expression during feather development. RESULTS: We conducted transcriptomic analysis of five zones of feather morphologies from two feather types at different times during their regeneration after plucking. The expression profiles of genes associated with the development of feather structure were examined. We compared the gene expression patterns in different types of feathers and different portions of a feather and identified morphotype-specific gene expression patterns. Many candidate genes were identified for growth control, morphogenesis, or the differentiation of specific structures of different feather types. CONCLUSION: This study laid the ground work for studying the evolutionary origin and diversification of feathers as abundant data were produced for the study of feather morphogenesis. It significantly increased our understanding of the complex molecular and cellular events in feather development processes and provided a foundation for future studies on the development of other skin appendages.

Genomic organization, transcriptomic analysis, and functional characterization of avian α- and ß-keratins in diverse feather forms.

Feathers are hallmark avian integument appendages, although they were also present on theropods. They are composed of flexible corneous materials made of α- and ß-keratins, but their genomic organization and their functional roles in feathers have not been well studied. First, we made an exhaustive search of α- and ß-keratin genes in the new chicken genome assembly (Galgal4). Then, using transcriptomic analysis, we studied α- and ß-keratin gene expression patterns in five types of feather epidermis. The expression patterns of ß-keratin genes were different in different feather types, whereas those of α-keratin genes were less variable. In addition, we obtained extensive α- and ß-keratin mRNA in situ hybridization data, showing that α-keratins and ß-keratins are preferentially expressed in different parts of the feather components. Together, our data suggest that feather morphological and structural diversity can largely be attributed to differential combinations of α- and ß-keratin genes in different intrafeather regions and/or feather types from different body parts. The expression profiles provide new insights into the evolutionary origin and diversification of feathers. Finally, functional analysis using mutant chicken keratin forms based on those found in the human α-keratin mutation database led to abnormal phenotypes. This demonstrates that the chicken can be a convenient model for studying the molecular biology of human keratin-based diseases.

Genome-wide patterns of genetic variation in two domestic chickens.

Domestic chickens are excellent models for investigating the genetic basis of phenotypic diversity, as numerous phenotypic changes in physiology, morphology, and behavior in chickens have been artificially selected. Genomic study is required to study genome-wide patterns of DNA variation for dissecting the genetic basis of phenotypic traits. We sequenced the genomes of the Silkie and the Taiwanese native chicken L2 at ∼23- and 25-fold average coverage depth, respectively, using Illumina sequencing. The reads were mapped onto the chicken reference genome (including 5.1% Ns) to 92.32% genome coverage for the two breeds. Using a stringent filter, we identified ∼7.6 million single-nucleotide polymorphisms (SNPs) and 8,839 copy number variations (CNVs) in the mapped regions; 42% of the SNPs have not found in other chickens before. Among the 68,906 SNPs annotated in the chicken sequence assembly, 27,852 were nonsynonymous SNPs located in 13,537 genes. We also identified hundreds of shared and divergent structural and copy number variants in intronic and intergenic regions and in coding regions in the two breeds. Functional enrichments of identified genetic variants were discussed. Radical nsSNP-containing immunity genes were enriched in the QTL regions associated with some economic traits for both breeds. Moreover, genetic changes involved in selective sweeps were detected. From the selective sweeps identified in our two breeds, several genes associated with growth, appetite, and metabolic regulation were identified. Our study provides a framework for genetic and genomic research of domestic chickens and facilitates the domestic chicken as an avian model for genomic, biomedical, and evolutionary studies.

Tangy scent in Toona sinensis (Meliaceae) leaflets: isolation, functional characterization, and regulation of TsTPS1 and TsTPS2, two key terpene synthase genes in the biosynthesis of the scent compound.

Toona sinensis (Chinese Mahogany; Meliaceae), a subtropical deciduous tree, has a tangy scent resembling a mix of shallots and garlic. T. sinensis has long been known for its medicinal efficacy for treating enteritis, dysentery, itch and some cancers. However, its volatile components and their biosynthesis remain unexamined. In this study, we identified the spectrum of volatile compounds, isolated and functionally characterized two terpene synthase genes, Tstps1 and Tstps2, responsible for terpenoid synthesis in T. sinensis leaflets. TsTPS1 and TsTPS2 afford multiple products upon incubation with geranyl and farnesyl diphosphate respectively and mainly regulate the biosynthesis of (+) limonene and ß- elemene in vitro, respectively. Headspace analyses show that 98% of leaflet volatiles were sesquiterpenoids and the developing leaflets released a greater diversity and quantity of volatiles than the mature leaflets did, and that ß-elemene was the dominant component in both of them. These data suggested that tangy scent of T. sinensis consists of a combination of terpenoids and that Tstps2 was the major gene involved in the terpenoid biosynthesis in T. sinensis. In situ hybridization revealed that glandular cells of the leaf rachises accumulated abundant Tstps1 mRNA transcripts. Our GFP-based assay further unprecedentedly demonstrated that the transit-peptide of TsTPS1 targets specifically to the mitochondria.

Functional characterization of cellulases identified from the cow rumen fungus Neocallimastix patriciarum W5 by transcriptomic and secretomic analyses.

BACKGROUND: Neocallimastix patriciarum is one of the common anaerobic fungi in the digestive tracts of ruminants that can actively digest cellulosic materials, and its cellulases have great potential for hydrolyzing cellulosic feedstocks. Due to the difficulty in culture and lack of a genome database, it is not easy to gain a global understanding of the glycosyl hydrolases (GHs) produced by this anaerobic fungus. RESULTS: We have developed an efficient platform that uses a combination of transcriptomic and proteomic approaches to N. patriciarum to accelerate gene identification, enzyme classification and application in rice straw degradation. By conducting complementary studies of transcriptome (Roche 454 GS and Illumina GA IIx) and secretome (ESI-Trap LC-MS/MS), we identified 219 putative GH contigs and classified them into 25 GH families. The secretome analysis identified four major enzymes involved in rice straw degradation: ß-glucosidase, endo-1,4-ß-xylanase, xylanase B and Cel48A exoglucanase. From the sequences of assembled contigs, we cloned 19 putative cellulase genes, including the GH1, GH3, GH5, GH6, GH9, GH18, GH43 and GH48 gene families, which were highly expressed in N. patriciarum cultures grown on different feedstocks. CONCLUSIONS: These GH genes were expressed in Pichia pastoris and/or Saccharomyces cerevisiae for functional characterization. At least five novel cellulases displayed cellulytic activity for glucose production. One ß-glucosidase (W5-16143) and one exocellulase (W5-CAT26) showed strong activities and could potentially be developed into commercial enzymes.