Molecular study of the transcription factor SKN-1 and its putative relationship with genes that encode GST and antioxidant enzymes in Haemonchus contortus.

Haemonchus contortus is a parasitic nematode of ruminants. Once inside its host, it is exposed to reactive oxidative species and responds by synthesising antioxidant enzymes as a defence. In Caenorhabditis elegans, antioxidant genes are regulated by the transcription factor skinhead-1 (Cel-SKN-1). However, there is little information about the function of SKN-1 in H. contortus (Hco-SKN-1). Therefore, we performed a molecular investigation to characterise Hco-SKN-1 and its putative relationship with genes encode antioxidant enzymes, namely glutathione S-transferases (Hco-GSTs, n = 3), superoxide dismutase (Hco-SOD) and catalase (Hco-CAT), which are involved in haematophagy and defence against the host. We used in silico sequence analysis of Hco-SKN-1 and Hco-GSTs to design and perform relative expression assays involving H. contortus eggs, infective larvae (L 3 ) and adults. Furthermore, we exposed H. contortus transitional infective larvae (xL 3 ) to erythrocytes or hydrogen peroxide (H 2 O 2 ) and evaluated the relative expression of antioxidant genes at 24 or 48 h. Gene Ontology (GO) analysis revealed 31 functions associated with Hco-SKN-1 and Hco-GSTs, including stress resistance, larval development and the active immune response. Hco-GST-5957 and Hco-SOD showed the highest expression in adults, indicating a relationship with specific functions at this mature stage. xL 3 exposed to erythrocytes or H 2 O 2 showed significant upregulation of Hco-SKN-1, but it occurred after upregulation of the antioxidant genes, indicating that these genes are not regulated by Hco-SKN-1 during the blood-feeding stage. Additional investigation is necessary to understand the putative regulation of antioxidant genes by Hco-SKN-1 during the blood-feeding stage.