Genetic Variability And SNP Screening In P-glycoprotein Gene Of Haemonchus Contortus

Haemonchus contortus disease, also known as twisting stomach disease, which is caused by Haemonchus contortus in true stomach and small intestine of sheep, cattle and other ruminant stomach animals. The disease has occurred in the world, often resulting in anemia, edema, weakness and digestive disorders in grazing animals, and causing huge economic losses to the livestock industry. Currently, anti-worm drugs are still the main treatment of Haemonchus contortus disease, and frequent use of drugs make it possible that Haemonchus contortus become more resistant to drugs. For this reason, it is of great importance to find the drug resistance marker molecules based on the drug resistant mechanism of Haemonchus contortus. Actually, the research of drug resistance and genetic variability is connected closely. Research has revealed that, a wide range of geographic isolation plays an important role in population genetic variability. The research of population genetic variability will surely provide pivotal clues in genetic differentiation among populations and drug resistance mechanisms. Currently, the approach of population genetic variability and drug resistance mechanisms mainly based on the single characteristic marker loci technology, which including microsatellite, mitochondrial and ribosome genes. However, the defect of these means is obvious. No doubt, it is necessary to choose large sample for repeated several times experiments.What’s more important, the resistance to drugs usually relate to multiple genes and characters. So it is an urgent problem to screen the multiple mutated genes. In recent years, the development of next-generation sequencing provides an excellent platform for the research of multiple genes related with complex characters. Under such circumstance, this study used high-throughput sequencing methods in the genome of Haemonchus contortus to assess the level of single nucleotide polymorphism(SNP) by sites of nucleotide differences in order to explore the population genomics of Haemonchus contortus, and with such approach, it is practical to assess population genetic diversity and screen gene or marker molecules associated with drug resistance mechanism.The SNP technology which is based on the second-generation sequencing technology, including sequencing, blasting and confirmation the location and type of SNP. The study presented the genetic variability and SNP of P-glycoprotein gene among Hubei province, Inner Mongolia province, Xizang province, Sichuan province populations in China, ivermectin resistance population in England, standard population in Australia. The result showed a low level of genetic differentiation appeared within populations; populations in China were at a moderate level genetic differentiation, and a high level genetic differentiation among ivermectin resistance population in England, populations in China and standard population in Australia. The result illustrated geographic isolation played an important role in genetic evolution. It demonstrated a high level genetic differentiation among populations from different countries due to a relative far distance, while a moderate level genetic differentiation among populations from China due to a relative close distance. It is essential to mention that population from Xizang province demonstrated a slightly high level genetic differentiation with other sensitive populations from China, which was most likely the result of its unique plateau geographical environment and climatic conditions. Meanwhile, two SNPs connected with ivermectin resistance mechanisms were screened between the sensitive populations and ivermectin resistance populations. The location was scaffold HF967529.1,NO.84514 which mutated from Cytosine(C) to Adenine(A) at intron space of P-glycoprotein gene, and the other was the same scaffold HF967529.1, NO.38989 which mutated from Thymine(T) to Cytosine(C) near the P-glycoprotein gene. Additionally, the research could provide basic data for genetic structure characteristic analysis and screening gene or marker molecules associated with drug resistance mechanism on the whole genomic level of Haemonchus contortus.