1. Antibacterial peptide defensin is involved in midgut immunity of the soft tick, Ornithodoros moubata
Y Nakajima, A van der Goes van Naters-Yasui, D Taylor, M Yamakawa Insect Mol Biol. 2002 Dec;11(6):611-8. doi: 10.1046/j.1365-2583.2002.00372.x.
Two defensin genes A and B were previously demonstrated to be up-regulated by blood feeding in the soft tick, Ornithodoros moubata [Nakajima et al. (2001) Two isoforms of a member of the arthropod defensin family from the soft tick, Ornithodoros moubata (Acari: Argasidae). Insect Biochem Mol Biol 31: 747-751]. In this study, two defensin isoforms C and D similar to defensins A and B were newly cloned. A total of four defensins have been identified in O. moubata. All four Ornithodoros defensins are coded as prepro-defensins. Ornithodoros defensin genes consist of four exons and three introns, an organization reported in mussel defensins but not insect defensins. Ornithodoros defensin C and D genes are predominantly expressed in the midgut and up-regulated in response to blood feeding. The mature peptide of the previously cloned Ornithodoros defensin A was purified from the midgut lumen, indicating defensin is secreted into the midgut. These findings confirm the involvement of Ornithodoros defensin in midgut immunity.
2. Involvement of antibacterial peptide defensin in tick midgut defense
Yoshiro Nakajima, Demar Taylor, Minoru Yamakawa Exp Appl Acarol. 2002;28(1-4):135-40. doi: 10.1023/a:1025399610947.
Animals are constantly threatened by pathogenic microorganisms and have developed cellular and humoral immune responses to combat these infections. Invertebrates possess only an innate non-specific immune response. Antimicrobial substances are major components of innate immunity not only in invertebrates but also in vertebrates. Despite the importance of ticks as vectors of disease very little is known about their immune system. Our recent studies have revealed that four defensin isoforms are present in Ornithodoros moubata. These four isoforms are constitutively expressed in the midgut and up-regulated in response to blood feeding. Moreover, a mature peptide of defensin isoform A has been isolated from the tick midgut lumen. These findings indicate Ornithodoros defensins are involved in tick midgut defense against potentially harmful invasive microbes.
3. Molecular characterization of a defensin gene from a hard tick, Dermacentor silvarum
Juanjuan Wang, Gang Bian, Wen Pan, Tingting Feng, Jianfeng Dai Parasit Vectors. 2015 Jan 15;8:25. doi: 10.1186/s13071-014-0625-0.
Background: Ticks are distributed worldwide and considered as vectors of many human diseases. Tick defensins, a family of antimicrobial peptides, form the first line of defense against pathogens. Findings: A defensin-like gene, named Ds-defensin, was identified from a cDNA library of the hard tick Dermacentor silvarum collected from northeast China. The full-length cDNA of Ds-defensin was 225 bp, encoding a 74 amino acid peptide. The nucleotide sequence of Ds-defensin shared 98.2% similarity to putative defensin from Dermacentor marginatus. RT-PCR results suggested that Ds-defensin was extensively expressed in tick salivary gland and midgut, with a higher expression level in midgut. Ds-defensin showed broad antimicrobial activity against various Gram-positive and Gram-negative bacteria, as well as the fungus Candida albicans. Conclusions: We characterized a functional defensin from D. silvarum of China. Ds-defensin showed bactericidal activity against various Gram-positive and Gram-negative bacteria. Ds-defensin can be expected to be introduced to the medical field as a new molecule with antibacterial activity.
