Evaluation of DNA methylation and mRNA expression of heat shock proteins in thermal manipulated chicken.

Thermal manipulation during embryogenesis has been demonstrated to enhance the thermotolerance capacity of broilers through epigenetic modifications. Heat shock proteins (HSPs) are induced in response to stress for guarding cells against damage. The present study investigates the effect of thermal conditioning during embryogenesis and thermal challenge at 42 days of age on HSP gene and protein expression, DNA methylation and in vitro luciferase assay in brain tissue of Naked Neck (NN) and Punjab Broiler-2 (PB-2) chicken. On the 15th day of incubation, fertile eggs from two breeds, NN and PB-2, were randomly divided in to two groups: control (C)-eggs were incubated under standard incubation conditions, and thermal conditioning (TC)-eggs were exposed to higher incubation temperature (40.5°C) for 3 h on the 15th, 16th, and 17th days of incubation. The chicks obtained from each group were further subdivided and reared under different environmental conditions from the 15th to the 42nd day as normal [N; 25 ± 1 °C, 70% relative humidity (RH)] and heat exposed (HE; 35 ± 1 °C, 50% RH) resulting in four treatment groups (CN, CHE, TCN, and TCHE). The results revealed that HSP promoter activity was stronger in CHE, which had lesser methylation and higher gene expression. The activity of promoter region was lesser in TCHE birds that were thermally manipulated at the embryonic stage, thus reflecting their stress-free condition. This was confirmed by the lower level of mRNA expression of all the HSP genes. In conclusion, thermal conditioning during embryogenesis has a positive impact and improves chicken thermotolerance capacity in postnatal life.

Molecular Characterization of Thermostable Newcastle disease virus Isolated from Pigeon.

The HN and L gene sequences of an Indian isolate of Newcastle disease virus was analyzed prior to and after exposure to 56 °C at tenth passage and fifteenth passage to study the variations at molecular level. In the HN gene sequence of progenitor and thermostable strain, substitution of K373I, F374L, M516R, D517V were considered to contribute to the increase in the stability of the protein. In the L gene of the thermostable strain, variations were observed at many positions and among these the substitutions at position P675H K677R, K893D, R1132K, had charged amino acids, and at L656A, F657V, F869L, T886I, M899I, G1131V, V1675L, had hydrophobic amino acids that could be related to increased stability of L protein at high temperatures. The changes in amino acid sequence in HN and L gene of the thermostable strain might render structural variations that might have contributed to the stability of the strain at higher temperature.