Biswajit Brahma

The study was carried out to compare the in vitro and in vivo heat shock responses of cattle and buffaloes. The expression of heat responsive genes (HSP70 and HSF family) were studied in vitro in peripheral blood mononuclear cells (PBMCs) of cattle and buffalo. In vivo observations on animals were carried out to investigate the physiological responses of cattle and buffalo at different THI over a period of 14 months. The study indicated that onset and severity of heat stress at different THI varied significantly between cattle and buffalo. Rectal temperature (RT) showed a significant (p < 0.05) increase at THI 67 in buffaloes and at THI 68 in cattle. Significant (p < 0.01) differences in RT between the species were observed at THI 71, 72, and 73. Respiration rate (RR) significantly (p < 0.05) increased at THI 70 in both the species and significant (p < 0.05) differences in RR were observed between the species at THI 65, 68, 69, and 74. THI had significant (p < 0.05) effect on blood glucose and blood electrolytes of the species with increased levels at higher THI. Serum AST and ALT levels showed less pronounced changes over increasing THI. Heat stress-associated expressions of HSP 70 genes followed temporal changes with incremental THI. The expression of HSPA8 was consistent at lower THI whereas upregulation of HSPA1A and HSPA1L was evident at higher THI. The study concludes that changes in physiological parameters such as RT and RR occur in a phasic pattern in both species and onset of heat stress was early in buffalo as compared to cattle.

Meiotic recombination contributes to augmentation of genetic diversity, exclusion of deleterious alleles and proper segregation of chromatids. PRDM9 has been identified as the gene responsible for specifying the location of recombination hotspots during meiosis and is also the only known vertebrate gene associated with reproductive isolation between species. PRDM9 encodes a protein with a highly variable zinc finger (ZF) domain that varies between as well as within species. In the present study, the ZF domain of PRDM9 on chromosome 1 was characterized for the first time in 15 goat breeds and 25 sheep breeds of India. A remarkable variation in the number and sequence of ZF domains was observed. The number of ZF repeats in the ZF array varied from eight to 12 yielding five homozygous and 10 heterozygous genotypes. The number of different ZF domains was 84 and 52 producing 36 and 26 unique alleles in goats and sheep respectively. The posterior mean of dN/dS or omega values were calculated using the codeml tool of pamlx to identify amino acids that are evolving positively in goats and sheep, as positions −1, +3 and +6 in the ZF domain have been reported to experience strong positive selection across different lineages. Our study identified sites −5, −1, +3, +4 and +6 to be experiencing positive selection. Small ruminant zinc fingers were also found to be evolving under concerted evolution. Our results demonstrate the existence of a vast diversity of PRDM9 in goats and sheep, which is in concert with reports in many metazoans.

The copy number variation (CNV) is the number of copies of a particular gene in the genotype of an individual. Recent evidences show that the CNVs can vary in frequency and occurrence between breeds. These variations reportedly allowed different breeds to adapt to different environments. As copy number variations follow Mendelian pattern of inheritance, identification and distribution of these variants between populations can be used to infer the evolutionary history of the species. In this study, we have examined the absolute copy number of four Heat shock factor genes viz. HSF-1, 2, 4, and 5 in two different breeds of buffalo species using real-time PCR. Here, we report that the absolute copy number of HSF2 varies between the two breeds. In contrast no significant difference was observed in the copy number for HSF-1, 4, and 5 between the two breeds. Our results provide evidence for the presence of breed specific differences in HSF2 genomic copy number. This seems to be the first step in delineating the genetic factors underlying environmental adaptation between the two breeds. Nevertheless, a more detailed study is needed to characterize the functional consequence of this variation.