P-Glycoprotein Genes in Haemonchus Contortus

Abstract

Control of Haemonchus contortus currently relies on anthelmintics includingivermectin (IVM). The existence of IVM resistance threatens the sheep industry.Detailed knowledge of the underlying genetic mechanisms may revealopportunities to avoid selection of IVM resistance. Molecular tests are required inorder to more sensitively identify and quantify resistance and then test competinghypotheses on the prevention and control of resistance. It is first necessary toidentify those genes or loci under selection following IVM application and detectgenotypic markers of IVM resistance.However, as the genetic basis of IVM resistance is not yet established and in theabsence of genomic tools currently available for H. contortus, the approach takento date is the analysis of the gene families implicated in IVM resistance includingthe P‑glycoproteins (P‑gps). H. contortus has an incomplete genome withoutannotation and only one P‑gp messenger RNA (mRNA) transcript has been fullysequenced. The aim of this project was to discover the incomplete and dispersedP‑gp genetic sequences in the sequence databases and construct the putativegenes.Bioinformatics was used to reveal H. contortus sequences that map both from andto known P‑gp sequences in Caenorhabditis elegans by a process of Basic LocalAlignment Search Tool (BLAST) algorithms, protein distance matrices,phylogenetics and gene structure prediction algorithms. Evidence of up to 11P‑gp genes (pgp) was discovered, which is fewer than the 15 in C. elegans.There are eight clades in C. elegans (Cel‑pgp‑1; 2; 3/4; 5/6/7/8; 9; 10; 11;12/13/14/15) of which seven have representatives in H. contortus; there are nohomologues to the entire clade of four genes Cel‑pgp‑5 to 8 inclusive. All theduplications in C. elegans are on the X chromosome but none of these groups hasmore than one homologue in H. contortus. Conversely autosomal Cel‑pgp‑2 andCel‑pgp‑9 with evidence of multiple homologues in H. contortus are not duplicatedin C. elegans.

Date of Award	31 Dec 2013
Original language	English
Awarding Institution	University of Bath
Supervisor	Nicholas Priest (Supervisor), Adrian Wolstenholme (Supervisor), T. Walsh (Supervisor) & G. Coles (Supervisor)