Polymorphisms of BoLA-DRB 3.2 gene and associated genetic relationship among four strains of Tanzania shorthorn zebu cattle

Abstract

Bovine Lymphocyte Antigen (BoLA) genes play important roles in resistance or susceptibility of cattle to infectious diseases. The BoLA gene comprises of several loci including the most polymorphic site namely DRB 3.2. We amplified 200 DNA samples and sequenced 270 bp comprising exon 2 of BoLA-DRB 3.2 in four strains of Tanzania shorthorn zebu (TSZ) cattle (Tarime, Sukuma, Maasai, Singida white) and one breed, namely Friesian. Sequences were processed on Finch TV, aligned on Basic Local Alignment Search Tool (BLAST), and matched to amino acids using MEGA 6. Frequency of each allele was computed as proportion of total alleles in each population. Chi-square was used to test significance in allele frequencies. Heterozygosities were computed using Poptree 2. Putative evolutionary relationships were evaluated by Nei genetic distances. Thirty four alleles were determined, of which nine alleles are novel. The greatest number of alleles was determined in Tarime and Singida white and the lowest in Friesian. Heterozygosities were high within the animals. Phylogenetic tree showed two major clusters one for TSZ and a second for Friesian. Polymorphism at DRB 3.2 in TSZ could be one explanation for their ability to withstand various diseases and we recommend further evaluations in the breed.