Genome-wide scan for selection signatures and genes related to heat tolerance in domestic chickens in the tropical and temperate regions in Asia.

Heat stress is one of the major environmental stressors challenging the global poultry industry. Identifying the genes responsible for heat tolerance is fundamentally important for direct breeding programs. To uncover the genetic basis underlying the ambient temperature adaptation of chickens, we analyzed a total of 59 whole genomes from indigenous chickens that inhabit South Asian tropical regions and temperate regions from Northern China. We applied FST and π-ratio to scan selective sweeps and identified 34 genes with a signature of positive selection in chickens from tropical regions. Several of these genes are functionally implicated in metabolism (FABP2, RAMP3, SUGCT, and TSHR) and vascular smooth muscle contractility (CAMK2), and they may be associated with adaptation to tropical regions. In particular, we found a missense mutation in thyroid-stimulating hormone receptor (41020238:G>A) that shows significant differences in allele frequency between the chicken populations of the two regions. To evaluate whether the missense mutation in TSHR could enhance the heat tolerance of chickens, we constructed segregated chicken populations and conducted heat stress experiments using homozygous mutations (AA) and wild-type (GG) chickens. We found that GG chickens exhibited significantly higher concentrations of alanine aminotransferase, lactate dehydrogenase, and creatine kinase than AA chickens under heat stress (35 ± 1°C) conditions (P < 0.05). These results suggest that TSHR (41020238:G>A) can facilitate heat tolerance and adaptation to higher ambient temperature conditions in tropical climates. Overall, our results provide potential candidate genes for molecular breeding of heat-tolerant chickens.

Interaction between anionic dyes and cationic flocculant P(AM-DMC) in synthetic solutions.

Copolymer of acrylamide and 2-[(methacryloyloxy)ethyl]trimethylammonium chloride [P(AM-DMC)] is found to be effective to combine anionic dyes with strong aqueous solubility. This work aims mainly at revealing the interaction between anionic dyes and [P(AM-DMC)] by running jar test, spectra analysis and equilibrium dialysis experiments. The results show that P(AM-DMC) effectively decolorizes the tested strong water soluble anionic dyes, such as acidic, reactive and direct dyes, from their aqueous solutions under mild acidic and neutral conditions. Higher cationicity and optimal dose of flocculant P(AM-DMC) have to be used to achieve satisfactory and effective decolorization. Comparison of IR spectra of dye, flocculant P(AM-DMC) and the floc formed indicates chemical interaction occurred between sulfonic groups of dye and quaternary ammonium of flocculant. Plots of r-logC suggest cooperative interaction exists evidently for some dyes tested. Addition of KCl or urea reduces binding extent evidently, which shows the importance of electrostatic and hydrophobic interaction. Therefore the interaction between dyes tested and P(AM-DMC) might be controlled by hydrophobic, cooperative interaction and energetic interaction which includes chemical and electrostatic interactions.