Ancient and modern DNA reveal dynamics of domestication and cross-continental dispersal of the dromedary

Dromedaries have been fundamental to the development of human societies in arid landscapes and for long-distance trade across hostile hot terrains for 3,000 y. Today they continue to be an important livestock resource in marginal agro-ecological zones. However, the history of dromedary domestication and the influence of ancient trading networks on their genetic structure have remained elusive. We combined ancient DNA sequences of wild and early-domesticated dromedary samples from arid regions with nuclear microsatellite and mitochondrial genotype information from 1,083 extant animals collected across the species’ range. We observe little phylogeographic signal in the modern population, indicative of extensive gene flow and virtually affecting all regions except East Africa, where dromedary populations have remained relatively isolated. In agreement with archaeological findings, we identify wild dromedaries from the southeast Arabian Peninsula among the founders of the domestic dromedary gene pool. Approximate Bayesian computations further support the “restocking from the wild” hypothesis, with an initial domestication followed by introgression from individuals from wild, now-extinct populations. Compared with other livestock, which show a long history of gene flow with their wild ancestors, we find a high initial diversity relative to the native distribution of the wild ancestor on the Arabian Peninsula and to the brief coexistence of early-domesticated and wild individuals. This study also demonstrates the potential to retrieve ancient DNA sequences from osseous remains excavated in hot and dry desert environments

Flexibility and viscometric studies of globular proteins ovalbumin and ovotransferrin

98-107The ultrasonic velocity, density and viscosity of two egg proteins, ovalbumin and ovotransferrin in phosphate buffer have been studied at the physiological pH values. The thermodynamic functions for unfolding, ellipticity, surface amino acid residues and compressibility have been obtained for thermal and chemical denaturation in these food proteins. The com-puted values of Huggin’s constant and shape factor, at a fixed ionic strength 0.16 M are found to be in agreement with the reported values for globular proteins. The slow increase in free-energy of unfolding with temperature at a fixed pH 7 sug-gests uncoiling and in turn, disappearance of biological activity. It has been observed that the effects of temperature and chemical denaturant on the native protein may give rise to different conformational states. In the presence of urea and so-dium dodecyl sulphate (SDS), the proteins gave the excessively denatured states at 25ºC and pH 7, in comparison to the thermal denatured state. The positive values of partial adiabatic compressibility βs over the temperature range 45-75ºC suggest the possibility of large internal flexibility in ovotransferrin than in ovalbumin

Data from: Ancient and modern DNA reveal dynamics of domestication and cross-continental dispersal of the dromedary

Dromedaries have been fundamental to the development of human societies in arid landscapes and for long-distance trade across hostile hot terrains for 3,000 y. Today they continue to be an important livestock resource in marginal agro-ecological zones. However, the history of dromedary domestication and the influence of ancient trading networks on their genetic structure have remained elusive. We combined ancient DNA sequences of wild and early-domesticated dromedary samples from arid regions with nuclear microsatellite and mitochondrial genotype information from 1,083 extant animals collected across the species’ range. We observe little phylogeographic signal in the modern population, indicative of extensive gene flow and virtually affecting all regions except East Africa, where dromedary populations have remained relatively isolated. In agreement with archaeological findings, we identify wild dromedaries from the southeast Arabian Peninsula among the founders of the domestic dromedary gene pool. Approximate Bayesian computations further support the “restocking from the wild” hypothesis, with an initial domestication followed by introgression from individuals from wild, now-extinct populations. Compared with other livestock, which show a long history of gene flow with their wild ancestors, we find a high initial diversity relative to the native distribution of the wild ancestor on the Arabian Peninsula and to the brief coexistence of early-domesticated and wild individuals. This study also demonstrates the potential to retrieve ancient DNA sequences from osseous remains excavated in hot and dry desert environments

Drom970_17msat

This data matrix contains the raw data of 17 microsatellite loci genotyped in 970 dromedaries from 36 populations worldwide