Tissue and life-stage distribution of a defensin gene in the Lone Star tick, Amblyomma americanum.
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.
Todd
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SM
Department of Biological Sciences, Old Dominion University, Norfolk, Virginia 23529, USA.
Sonenshine
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DE
Hynes
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WL
D000818:Animals; D001096:Arachnid Vectors / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D001483:Base Sequence; D017931:DNA Primers / Q000737:chemistry; D018076:DNA, Complementary / Q000235:genetics; D023082:Defensins / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics*; D015870:Gene Expression / Q000502:physiology*; D020869:Gene Expression Profiling / Q000662:veterinary; D026863:Ixodidae / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D008018:Life Cycle Stages / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
D017931:DNA Primers; D018076:DNA, Complementary; D023082:Defensins