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Molecular characterization, tissue-specific expression, and RNA knockdown of the putative heat shock cognate 70 protein from Rhipicephalus haemaphysaloides

Wang, Fangfang, Gong, Haiyan, Zhang, Houshuang, Zhou, Yongzhi, Cao, Jie, Zhou, Jinlin
Parasitology research 2019 v.118 no.5 pp. 1363-1370
Haemaphysalis, Rhipicephalus, adults, amino acids, blood, cDNA libraries, complementary DNA, engorgement, fat body, gene expression, gene targeting, heat stress, hematophagy, larvae, mammals, messenger RNA, midgut, molecular weight, mortality, nymphs, open reading frames, quantitative polymerase chain reaction, salivary glands, ticks, vaccines
Heat shock cognate 70-kDa protein (RH-Hsc70) was identified from a cDNA library synthesized from the sialotranscriptomes of unfed and fed Rhipicephalus haemaphysaloides. The RH-Hsc70 open reading frame is 1950 bp long and encodes a protein that is 649 amino acids in length, with a predicted molecular weight of 71.1 kDa and a theoretical pI of 5.43. RH-Hsc70 exhibits 98% amino acid identity with Hsc70 in Haemaphysalis flava and 83% identity with Hsc70 in arthropods and mammals. RH-Hsc70 was mainly expressed in nymphs and adult ticks, not in larvae. Real-time quantitative PCR analysis indicated that RH-Hsc70 mRNA expression was induced by blood feeding in adult ticks. In addition, RH-Hsc70 gene expression was higher in the ovaries of fed adult ticks than that in the midguts, salivary glands, and fat bodies of unfed or fed adult ticks. RH-Hsc70 gene knockdown inhibited tick blood feeding, significantly decreased tick engorgement rate, and increased tick death rate. These data illustrate the importance of RH-Hsc70 in tick blood feeding and aging, which makes it a promising candidate for the development of anti-tick vaccines.