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Tissue and life‐stage distribution of a defensin gene in the Lone Star tick, Amblyomma americanum
Author(s) -
TODD S. M.,
SONENSHINE D. E.,
HYNES W. L.
Publication year - 2007
Publication title -
medical and veterinary entomology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 82
eISSN - 1365-2915
pISSN - 0269-283X
DOI - 10.1111/j.1365-2915.2007.00682.x
Subject(s) - amblyomma americanum , biology , dermacentor variabilis , ixodes scapularis , tick , ixodidae , defensin , microbiology and biotechnology , gene , genetics , virology
The transcript sequence of the Amblyomma americanum Linnaeus (Acari: Ixodidae) defensin, termed amercin ( amn ), was ascertained and a 219‐bp amn coding region identified. The gene encodes a 72‐amino acid prepropeptide with a putative 37‐amino acid mature peptide. This gene shows little similarity to either of the defensins from Amblyomma hebraeum Koch, the only other Amblyomma species for which a defensin has been described. Sequence comparisons with other tick defensins reveal amn to be shorter (6 bp or 2 amino acids) than the Ixodes scapularis Linnaeus (Acari: Ixodidae) and Dermacentor variabilis (Say) (Acari: Ixodidae) defensin sequences. The amercin prepropeptide has 60.8% and 59.5% similarity with the I. scapularis and D. variabilis prepropeptides, respectively, whereas the mature amercin peptide has 73.7% and 71.1% similarity with the mature peptides of these ticks. Similarity with other tick defensins ranges from 42% to 71%. In A. americanum , defensin transcript was found in the midgut, fat body and salivary gland tissues, as well as in the haemocytes. Defensin transcript was also present in early‐stage eggs (less than 48 h old), late‐stage eggs (approximately 2 weeks old), larvae and nymphs of A. americanum and I. scapularis , both of which are vector‐competent for Borrelia spirochetes.