DETECTION OF AVIAN INFLUENZA RESISTANT GENE (MX GENE) AND ITS DIVERSITY IN DIFFERENT BREEDS OF CHICKEN AND DUCK

Abstract

Detection of Avian Influenza Resistant Gene (Mx gene) and its diversity in different breeds of chicken and duck by DR. Minakshi Nag. Livestock is an integral component of agricultural economy of Bangladesh providing food, nutrition, income, savings, etc. Presently, poultry meat and eggs provide the cheapest quality animal protein to the millions of people. However, this sector is facing a hazardous situation due to outbreak of avian influenza (AI) since 2007 and posing a great threat to the growing poultry industry. Overall, mutation of the virus in the face of any control approach remains the real challenge. Targeting Mx gene may be an approach for genetic breeding to develop avian influenza resistant poultry. The chicken Mx protein has been reported to exhibit antiviral activity against the influenza virus. Chicken Mx gene is highly polymorphic, and that a single-nucleotide polymorphism affecting amino acid 631 determines antiviral activity. But there is scarcity of information on Mx gene and its diversity in poultry in Bangladesh. Hence, present study was conducted to investigate the presence of Mxgene and their diversity in chicken and duck. A total of 60 blood samples were collected from six chicken breeds (Rhode Island Red, White Leghorn, White Rock, Barred Plymouth Rock, Necked Neck & Hilly) and 4 duck breeds (Pekin, Rupali, Nageshwari & Common Deshi). Genomic DNA were extracted from blood samples and the quality and quantity of extracted DNA were measured using Nano Drop spectrophotometer. Two sets of primers reported by Seyama et al., (2006) & Sironi et al., (2006) were used in PCR. By both sets of primers Mx gene was amplified from chicken and duck DNA. The overall detection rate was found to ranges from 43.64 to 75.68%. Among 2 sets of primer, one set reported by Seyama ef al., (2006) was found more sensitive than others reported by Sironi ef al., (2010). RFLP with RsaI and SsplI was conducted on the PCR products of mismatch primer reported by Seyama et al., (2006). A total of 27 PCR products were digested with restriction enzymes and of these 85.19% (23/27) were found to be digested either completely or partially with any of the restriction enzyme (Rsal and Sspl) used. But 14.81% (4/27) remain undigested with any of the restriction enzyme. From this digestion study it is revealed that tested chicken and duck samples contain diverse Mx gene allele. These are homozygous resistant (R/R), heterozygous (R/S) and homozygous sensitive (S/S). The average proportion of each Mxgene allele in the sampled birds (chicken and duck) are 22.22% homozygous resistant (R/R), 44.44% homozygous sensitive (S/S) and 18.52% heterozygous (R/S). In chicken the R/R, S/S and R/S Mx allelic gene was found 27.78, 33.33 and 16.67% respectively; while in duck it was 11.11% (R/R), 66.67% (S/S) and 22.22% (R/S). When looking minutely, it is observed that Mx gene diversity exists not only among the breeds and species but also within the individual. In the present study part of one Mx gene from indigenous Necked Neck chicken was sequenced (98bp) and compared with the sequences from Gene Bank. The maximum homology (95%) of this 98bp was found with the Mx gene from White Leghorn and other chicken Mx gene but phylogenetically clustered differently from them. From the present study it may be concluded that both chicken and duck containing Mx gene in their genome and variation of Mx gene exists within and among the breed/s and species. Though derived from indigenous chicken sequenced Mx gene had high homology with exotic White Leghorn. To the best of my knowledge this was the first study on Mx gene in Bangladesh covering both chicken and duck species. Moreover, the Mx gene sequence determined in the present study was the only one sequenced from Bangladesh.