Abstract The maintenance of major histocompatibility complex ( MHC ) polymorphism has been hypothesized to result from many mechanisms such as rare‐allele advantage , heterozygote advantage , and allele counting . In the study reported herein, 224 vulnerable Chinese egrets ( Egretta eulophotes ) were used to examine these hypotheses as empirical results derived from bird studies are rare. Parasite survey showed that 147 (65.63%) individuals were infected with 1–3 helminths, and 82.31% of these infected individuals carried Ascaridia sp. Using asymmetric polymerase chain reaction technique, 10 DAB 1, twelve DAB 2, and three DAB 3 exon 2 alleles were identified at each single locus. A significant association of the rare allele Egeu ‐ DAB 2*05 (allele frequency: 0.022) with helminth resistance was found for all helminths, as well as for the most abundant morphotype Ascaridia sp. in the separate analyses. Egeu ‐ DAB 2*05 occurred frequently in uninfected individuals, and individuals carrying Egeu ‐ DAB 2*05 had significantly lower helminth morphotypes per individual ( HMI ) (the number of HMI) and the fecal egg count values. Further, the parasite infection measurements were consistently lower in individuals with an intermediate number of different alleles in the duplicated DAB loci. Significantly, heterozygosity within each DAB locus was not correlated with any parasite infection measurements. These results indicate that the diversity in MHC Egeu ‐ DAB gene is associated with intestinal parasite load and maintained by pathogen‐driven selection that probably operate through both the rare‐allele advantage and the allele counting strategy , and suggest that Egeu ‐ DAB 2*05 might be a valuable indicator of better resistance to helminth diseases in the vulnerable Chinese egret.
Avian pathogenic Escherichia coli (APEC) is a subgroup of extra-intestinal pathogenic E. coli (ExPEC) strains that cause avian colibacillosis, resulting in significant economic losses to the poultry industry worldwide. It has been reported that a few two-component signal transduction systems (TCS) participate in the regulation of the virulence factors of APEC infection. In this study, a basSR-deficient mutant strain was constructed from its parent strain APECX40 (WT), and high-throughput sequencing (RNA-seq) was performed to analyse the transcriptional profile of WT and its mutant strain XY1. Results showed that the deletion of basSR down-regulated the transcript levels of a series of biofilm- and virulence-related genes. Results of biofilm formation assays and bird model experiments indicated that the deletion of basSR inhibited biofilm formation in vitro and decreased bacterial virulence and colonization in vivo. In addition, electrophoretic mobility shift assays confirmed that the BasR protein could bind to the promoter regions of several biofilm- and virulence-related genes, including ais, opgC and fepA. This study suggests that the BasSR TCS might be a global regulator in the pathogenesis of APEC infection. RESEARCH HIGHLIGHTSTranscriptional profiling showed that BasSR might be a global regulator in APEC.BasSR increases APEC pathogenicity in vivo.BasSR positively regulates biofilm- and the virulence-associated genes.BasSR can bind to the promoter regions of virulence-associated genes ais, opgC and fepA. Transcriptional profiling showed that BasSR might be a global regulator in APEC. BasSR increases APEC pathogenicity in vivo. BasSR positively regulates biofilm- and the virulence-associated genes. BasSR can bind to the promoter regions of virulence-associated genes ais, opgC and fepA.
Noninvasive and nondestructive DNA sampling techniques are becoming more important in genetic studies because they can provide genetic material from wild animals with less or even without disturbance, which is particularly useful for the study of endangered species, i.e., birds. However, nondestructively and noninvasively sampled DNA may, in some cases, be inadequate in the amount and quality of the material collected, which can lead to low amplification success rates and high genotyping errors. In this study, noninvasive (eggshell swab, shed feather and feces), nondestructive (plucked feather and buccal swab) and invasive (blood) DNA samples were collected from the vulnerable Chinese Egret (Egretta eulophotes). DNA concentrations, PCR amplification success and microsatellite genotyping errors of different sample types were evaluated and compared to determine whether noninvasive and nondestructive samples performed as well as invasive samples in our experimental procedures. A total of 159 samples were collected in the field. Among the different sample types, the highest DNA concentrations (154.0–385.5 ng/μL) were obtained from blood. Those extracted from fecal samples were the lowest, ranging from 1.25 to 27.5 ng/μL. Almost all of the DNA samples, i.e., 95.59 %, were successfully amplified for mtDNA (n = 152) and 92.76 % of mtDNA samples were successfully genotyped for at least five of the nine microsatellite loci tested (n = 141). Blood samples and buccal swabs produced reliable genotypes with no genotyping errors, but in feces, allelic dropouts and false alleles occurred in all nine loci, with error rates ranging from 6.67 to 38.10 % for the dropouts and from 6.06 to 15.15 % for the false alleles. These results indicate that both nondestructive and noninvasive samplings are suitable for avian microsatellite genotyping, save for fecal DNA. However, we should remain cautious of the appearance of genotyping errors, especially when using noninvasive material.
In this study,contents of heavy metal,copper(Cu),zinc(Zn),lead(Pb) and cadmium(Cd) were measured in the feather,muscle,bone,liver and heart of four species of raptors,Grass Owl(Tyto capensis),Oriental Scops Owl(Otus sunia),Eurasian Hobby(Falco subbuteo) and Common Kestrel(Falco tinnunculus),collected from Jimei area in Xiamen.The result showed that the heavy metal contents were ZnCuPbCd in the feather,muscle,liver and heart of Grass Owl and Oriental Scops Owl and in the five kinds of organs and tissues of Eurasian Hobby and Common Kestrel,and that the heavy metal contents were ZnCuPbCd in the bone of Grass Owl and Oriental Scops Owl.The copper,zinc,lead and cadmium were higher in the liver,heart and bone,but lower in the muscle of raptor birds.Heavy metal contents in the raptors were mainly affected by environmental pollution,food habit and the ability of collecting heavy metal of the birds.
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