Study of formation of green eggshell color in ducks through global gene expression.

The green eggshell color produced by ducks is a threshold trait that can be influenced by various factors, such as hereditary, environment and nutrition. The aim of this study was to investigate the genetic regulation of the formation of eggs with green shells in Youxian ducks. We performed integrative analysis of mRNAs and miRNAs expression profiling in the shell gland samples from ducks by RNA-Seq. We found 124 differentially expressed genes that were associated with various pathways, such as the ATP-binding cassette (ABC) transporter and solute carrier supper family pathways. A total of 31 differentially expressed miRNAs were found between ducks laying green eggs and white eggs. KEGG pathway analysis of the predicted miRNA target genes also indicated the functional characteristics of these miRNAs; they were involved in the ABC transporter pathway and the solute carrier (SLC) supper family. Analysis with qRT-PCR was applied to validate the results of global gene expression, which showed a correlation between results obtained by RNA-seq and RT-qPCR. Moreover, a miRNA-mRNA interaction network was established using correlation analysis of differentially expressed mRNA and miRNA. Compared to ducks that lay white eggs, ducks that lay green eggs include six up-regulated miRNAs that had regulatory effects on 35 down-regulated genes, and seven down-regulated miRNAs which influenced 46 up-regulated genes. For example, the ABC transporter pathway could be regulated by expressing gga-miR-144-3p (up-regulated) with ABCG2 (up-regulated) and other miRNAs and genes. This study provides valuable information about mRNA and miRNA regulation in duck shell gland tissues, and provides foundational information for further study on the eggshell color formation and marker-assisted selection for Youxian duck breeding.

[Cloning and polymorphism analysis of intron 2 of the GH gene in Takifugu].

Size and nucleotide polymorphisms of intron 2 of the growth hormone (GH) gene was studied in 82 individuals from Takifugu obscurus, Takifugu rubripes and Takifugu niphobles with PAGE, SSCP and cloning. Results showed that there were nine length variants (A~I) in these fishes, ranging from 271351 bp, with a frequency of variation of 24.22%. Sequence analysis of the 9 length variants showed the average percentages of the four bases (ATG and C) were 17.15, 20.77, 37.38 and 24.70, respectively, and the difference between GC content (45.47) and AT content (54.53) was not remarkable. Length variation was mainly due to the variable number of microsatellite TCTG repeats (N=20 approximately 40). Further sequence comparison revealed 4 substitution sites: a (C-->A) transversion at nucleotide 103 and 3 transitions 83(C-->T), 101(A-->G) and 296(G-->A), respectively. Phylogenetic analysis of these length variants placed DD and II into one group first, which was subsequently joined by GG and AA, BB and CC, EE and HH were then clustered together, FF was joined last. Thus, intraspecific variations were much smaller than interspecific variations for the intron 2 of the GH gene.