BACKGROUND: The strongylid nematode Haemonchus contortus is a parasite of major concern for modern livestock husbandry because hostile environmental conditions may induce diapause in the early fourth-stage larvae. METHODS: A new gene
Hc-daf-22 was identified which is the homologue of
Ce-daf-22 and human SCPx. Genome walking and RACE were performed to obtain the whole cDNA and genomic sequence of this gene. Using qRT-PCR with all developmental stages as templates to explore the transcription level and micro-injection was applied to confirm the promoter activity of the 5'-flanking region. Overexpression, rescue and RNA interference experiments were performed in N2,
daf-22 mutant (ok 693) strains of C. elegans to study the gene function of
Hc-daf-22. RESULTS: The full length gene of
Hc-daf-22 (6,939bp) contained 16 exons separated by 15 introns, and encoded a cDNA of 1,602bp (533 amino acids, estimated at about 59.3kDa) with a peak in L3 and L4 in transcriptional level. The Hc-DAF-22 protein was consisted of a 3-oxoacyl-CoA thiolase domain and a SCP2 domain and evolutionarily conserved. The 1,548bp fragment upstream of the 5'-flanking region was confirmed to have promoter activity compared with 5'-flanking region of
Ce-daf-22. The rescue experiment by micro-injection of
daf-22 (
ok693) mutant strain showed significant increase in body size and brood size in the rescued worms with significantly reduced or completely absent fat granules confirmed by Oil red O staining, indicating that
Hc-daf-22 could partially rescue the function of
Ce-daf-22. Furthermore, RNAi with
Hc-daf-22 could partially silence the endogenous
Ce-daf-22 in N2 worms and mimic the phenotype of
daf-22 (
ok693) mutants. CONCLUSION: The gene
Hc-daf-22 was isolated and its function identified using C. elegans as a model organism. Our results indicate that
Hc-daf-22 shared similar characteristics and function with
Ce-daf-22 and may play an important role in peroxisomal -oxidation and the development in H. contortus.