Tuoyu Geng

The mitochondrial genome sequence and molecular phylogeny of the turkey, Meleagris gallopavo.

The mitochondrial genome (mtGenome) has been little studied in the turkey (Meleagris gallopavo), a species for which there is no publicly available mtGenome sequence. Here, we used PCR-based methods with 19 pairs of primers designed from the chicken and other species to develop a complete turkey mtGenome sequence. The entire sequence (16,717 bp) of the turkey mtGenome was obtained, and it exhibited 85% similarity to the chicken mtGenome sequence. Thirteen genes and 24 RNAs (22 tRNAs and 2 rRNAs) were annotated. An mtGenome-based phylogenetic analysis indicated that the turkey is most closely related to the chicken, Gallus gallus, and quail, Corturnix japonica. Given the importance of the mtGenome, the present work adds to the growing genomic resources needed to define the genetic mechanisms that underlie some economically significant traits in the turkey.

Molecular Analysis of the Relatedness of Five Domesticated Turkey Strains

Our knowledge of the genetic relatedness among the eight existing domesticated turkey strains is limited. To begin to address this paucity, genetic relatedness among five turkey strains (Blue Slate, Bourbon Red, Narragansett, Royal Palm, and Spanish Black) was investigated using three molecular marker systems: randomly amplified polymorphic DNA (RAPD), microsatellite, and SNPs derived from a sequence tagged site and a cloned RAPD fragment. The RAPD analyses were based on five primers that revealed a total of 14 informative DNA fragments in all five populations. The microsatellite analyses involved two informative alleles from three primer-pairs. A total of nine SNPs were detected, one of which appeared to be strain specific. This SNP formed the basis of a PCR-RFLP genotyping procedure developed to distinguish one of the strains from the other four. Evidence from these analyses including the SNP-based RFLP-PCR suggests that Royal Palm is distinct from the other four strains, though more closely related to Narragansett. These data provide, for the first time, molecular evidence of the potential relationships among noncommercial domesticated turkey strains.

Screening for genes involved in antibody response to sheep red blood cells in the chicken, Gallus gallus

Antibody response, an important trait in both agriculture and biomedicine, plays a part in protecting animals from infection. Dissecting molecular basis of antibody response may improve artificial selection for natural disease resistance in livestock and poultry. A number of genetic markers associated with antibody response have been identified in the chicken and mouse by linkage-based association studies, which only define genomic regions by genetic markers but do not pinpoint genes for antibody response. In contrast, global expression profiling has been applied to define the molecular bases of a variety of biological traits through identification of differentially expressed genes (DEGs). Here, we employed Affimetrix GeneChip Chicken Genome Arrays to identify differentially expressed genes for antibody response to sheep red blood cells (SRBC) using chickens challenged with and without SRBC or chickens with high and low anti-SRBC titers. The DEGs include those with known (i.e., MHC class I and IgH genes) or unknown function in antibody response. Classification test of these genes suggested that the response of the chicken to intravenous injection of SRBC involved multiple biological processes, including response to stress or other different stimuli, sugar, carbohydrate or protein binding, and cell or soluble fraction, in addition to antibody response. This preliminary study thus provides an insight into molecular basis of antibody response to SRBC in the chicken.

Mitochondrial DNA-Based Analyses of Relatedness Among Turkeys, Meleagris gallopavo

The domesticated turkey, Meleagris gallopavo, is believed to be a single breed with several varieties whose relatedness and origins remain poorly understood. Using the mitochondrial genome sequence (GenBank accession no. EF153719) that our group first reported, we investigated the relationships among 15 of the most widely occurring turkey varieties using D-loop and 16S RNA sequences. We included, as a non-traditional outgroup, mtDNA sequence information from wild turkey varieties. A total of 24 SNPs, including 18 in the D-loop and 6 in the 16S rRNA, was identified, validated and used. Of the 15 haplotypes detected based on these SNPs, 7 were unique to wild turkeys. Nucleotide diversity estimates were relatively low when compared to those reported for chickens and other livestock. Network and phylogenetic analyses showed a closer relationship among heritage varieties than between heritage and wild turkeys. The mtDNA data provide additional evidence that suggest a recent divergence of turkey varieties.

Characterization of expressed sequence tags from a gallus gallus pineal gland cDNA library

The pineal gland is the circadian oscillator in the chicken, regulating diverse functions ranging from egg laying to feeding. Here, we describe the isolation and characterization of expressed sequence tags (ESTs) isolated from a chicken pineal gland cDNA library. A total of 192 unique sequences were analysed and submitted to GenBank; 6% of the ESTs matched neither GenBank cDNA sequences nor the newly assembled chicken genomic DNA sequence, three ESTs aligned with sequences designated to be on the Z_random, while one matched a W chromosome sequence and could be useful in cataloguing functionally important genes on this sex chromosome. Additionally, single nucleotide polymorphisms (SNPs) were identified and validated in 10 ESTs that showed 98% or higher sequence similarity to known chicken genes. Here, we have described resources that may be useful in comparative and functional genomic analysis of genes expressed in an important organ, the pineal gland, in a model and agriculturally important organism.