Comparative FISH mapping suggests poor conservation between chicken and duck genes

Differential cellular immune responses between chickens and ducks to H9N2 avian influenza virus infection

Avian influenza is an important infectious disease for the poultry industry and an ongoing public health concern. In this study, monoclonal antibodies (mAbs) specific to duck CD3ɛ, CD4 and CD8α were generated by immunizing mice with the corresponding Escherichia coli-expressed proteins and producing hybridomas. The resulting mAbs were used to investigate cellular immune responses of ducks and chickens during H9N2 avian influenza A virus (AIV) infection. By flow cytometric analysis, responses of T lymphocytes, especially CD8(+), CD8(+)CD25(+) and CD4(+)CD25(+) T cells, were stronger in ducks than in chickens following H9N2 AIV-infection. By quantitative real-time PCR analysis, virus mRNA could be detected in cloaca and oropharynx from both bird species and in spleens from chickens, and distinctive kinetics of transcriptional levels of interleukins and interferons were exhibited between chickens and ducks. With ducks showing more active and robust cellular immune responses than chickens, these results revealed that the distinct responses to H9N2 AIV infection may contribute to the different susceptibilities to AIV infection between the two species.

Methionine metabolism in piglets Fed DL-methionine or its hydroxy analogue was affected by distribution of enzymes oxidizing these sources to keto-methionine

Previous evidence shows that the extensive catabolism of dietary essential amino acids (AA) by the intestine results in decreased availability of these AA for protein synthesis in extraintestinal tissues. This raises the possibility that extraintestinal availability of AA may be improved by supplying the animal with an AA source more of which can bypass the intestine. To test this hypothesis, six barrows (35-day-old, 8.6 +/- 1.4 kg), implanted with arterial, portal, and mesenteric catheters, were fed a DL-methionine (DL-MET) or DL-2-hydroxy-4-methylthiobutyrate (DL-HMTB) diet once hourly and infused intramesenterically with 1% p-amino hippurate. Although the directly available L-MET in DL-MET diet was about 1.2-fold that in DL-HMTB diet, the net portal appearance of L-MET was not different between the two diets. Compared with the low mRNA abundance and low activity of D-2-hydroxy acid dehydrogenase (D-HADH) and l-2-hydroxy acid oxidase (L-HAOX) in the intestine, the high mRNA abundance and high activity of D-AA oxidase (D-AAOX) indicated that the intestine had a relatively higher capacity of D-MET utilization than of dl-HMTB utilization to L-MET synthesis and its subsequent metabolism. However, in contrast to the much lower D-AAOX activity (nmol/g tissue) in the stomach than in the liver and kidney, both d-HADH and L-HAOX activity in the stomach was comparable with those in the liver and/or kidney, indicating the substantial capacity of the stomach to convert DL-HMTB to L-MET. Collectively, the difference in distribution of activity and mRNA abundance of D-AAOX, D-HADH, and L-HAOX in the piglets may offer a biological basis for the similar portal appearance of L-MET between DL-MET and DL-HMTB diets, and thus may provide new important insights into nutritional efficiency of different L-MET sources.

FISH mapping of 57 BAC clones reveals strong conservation of synteny between Galliformes and Anseriformes

Karyotypes of chicken (Gallus gallus domesticus; 2n = 78) and mallard duck (Anas platyrhynchos; 2n = 80) share the typical organization of avian karyotypes including a few macrochromosome pairs, numerous indistinguishable microchromosomes, and Z and W sex chromosomes. Previous banding studies revealed great similarities between chickens and ducks, but it was not possible to use comparative banding for the microchromosomes. In order to establish precise chromosome correspondences between these two species, particularly for microchromosomes, we hybridized 57 BAC clones previously assigned to the chicken genome to duck metaphase spreads. Although most of the clones showed similar localizations, we found a few intrachromosomal rearrangements of the macrochromosomes and an additional microchromosome pair in ducks. BAC clones specific for chicken microchromosomes were localized to separate duck microchromosomes and clones mapping to the same chicken microchromosome hybridized to the same duck microchromosome, demonstrating a high conservation of synteny. These results demonstrate that the evolution of karyotypes in avian species is the result of fusion and/or fission processes and not translocations.

Molecular cloning and expression of the duplicated thyroid hormone responsive spot 14 (THRSP) genes in ducks

Thyroid hormone responsive Spot 14 (THRSP) is suggested as a transcription factor involved in the regulation of adipogenic enzymes by 3 thyroid response elements in the promoter region. In the chicken genome, THRSP gene was identified to duplicate into 2 paralogs, THRSPalpha and THRSPbeta. In the current study, cDNA sequences of the duplicated duck THRSP genes were cloned by real-time PCR and rapid amplification of cDNA ends. Duck THRSPalpha and THRSPbeta were predicted to encode peptides with 133 amino acids, which had 74 and 68% sequence identity at cDNA level, 78 and 74% identity at amino acid level to the chicken counterparts, respectively. A high percentage (73.1%) of G and C nucleotides were found in the 3' untranslated region of duck THRSPbeta cDNA. Although a low similarity of peptide composition was shared between ducks and mammals, and a moderate similarity was shared between ducks and chickens, many predicted properties of THRSP, including the pI, subcellular localization and functional domains seemed to be highly conserved. The present study demonstrated that the duck THRSP gene duplicates into the 2 paralogs as in chickens. Phylogenetic analysis indicated that the duplication for THRSP paralogs appeared to have taken place preceding the chicken-duck split, and the diverging rate between THRSP paralogs seemed faster in the chicken genome than that in the duck genome. Expression analysis by real-time quantitative PCR showed that THRSP paralogs in ducks were more actively transcribed in fat tissues (i.e., s.c. fat and abdominal fat) than in liver, and the mRNA concentrations of THRSPbeta were higher than that of THRSPalpha in liver and s.c. fat.