Molecular characterization and functional analysis of Eimeria tenella malate dehydrogenase

Eimeria tenella is a serious intracellular parasite that actively invades cecal epithelial cells of chickens. The widespread use of drugs causes severe resistance to Eimeria tenella . We detected that malate dehydrogenase (MDH), one of the differentially expressed genes, was upregulated in diclazuril-resistant and maduramicin-resistant strains through transcriptome sequencing. In this study, we cloned and expressed MDH of E. tenella ( Et MDH). Quantitative real-time polymerase chain reactions (qPCR) and Western blots were used to analyze the expression of Et MDH in resistant and sensitive strains, indicating Et MDH was upregulated in two resistant strains at the messenger RNA and protein levels. Enzyme activity was tested through absorbance measurement and the Et MDH activity increased in two resistant strains. Expression levels of Et MDH in four developmental stages of E. tenella were tested through qPCR and Western blot. Invasion inhibition assays explored if Et MDH was involved in invasion of DF-1 cells by E. tenella sporozoites. Indirect immunofluorescence assays investigated Et MDH distribution during parasite development in DF-1 cells invaded by E. tenella sporozoites. Experimental results showed that Et MDH may be related to drug resistance of E. tenella during its development and invasion . Et MDH may be an effective molecular marker for detection of E. tenella drug resistance.