Vector Biology Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, Rockville, Maryland, USA.
PLoS One. 2012;7(9):e44612. doi: 10.1371/journal.pone.0044612. Epub 2012 Sep 25.
Saliva of hematophagous arthropods contains a diverse mixture of compounds that counteracts host hemostasis. Immunomodulatory and antiinflammatory components are also found in these organisms' saliva. Blood feeding evolved at least ten times within arthropods, providing a scenario of convergent evolution for the solution of the salivary potion. Perhaps because of immune pressure from hosts, the salivary proteins of related organisms have considerable divergence, and new protein families are often found within different genera of the same family or even among subgenera. Fleas radiated with their vertebrate hosts, including within the mammal expansion initiated 65 million years ago. Currently, only one flea species-the rat flea Xenopsylla cheopis-has been investigated by means of salivary transcriptome analysis to reveal salivary constituents, or sialome. We present the analysis of the sialome of cat flea Ctenocephaides felis.
A salivary gland cDNA library from adult fleas was randomly sequenced, assembled, and annotated. Sialomes of cat and rat fleas have in common the enzyme families of phosphatases (inactive), CD-39-type apyrase, adenosine deaminases, and esterases. Antigen-5 members are also common to both sialomes, as are defensins. FS-I/Cys7 and the 8-Cys families of peptides are also shared by both fleas and are unique to these organisms. The Gly-His-rich peptide similar to holotricin was found only in the cat flea, as were the abundantly expressed Cys-less peptide and a novel short peptide family.
CONCLUSIONS/SIGNIFICANCE: Fleas, in contrast to bloodsucking Nematocera (mosquitoes, sand flies, and black flies), appear to concentrate a good portion of their sialome in small polypeptides, none of which have a known function but could act as inhibitors of hemostasis or inflammation. They are also unique in expansion of a phosphatase family that appears to be deficient of enzyme activity and has an unknown function.
吸血节肢动物的唾液中含有多种化合物，可阻止宿主止血。这些生物的唾液中还含有免疫调节和抗炎成分。在节肢动物中，吸血至少进化了十次，为唾液配方的趋同进化提供了一个场景。也许是因为宿主的免疫压力，相关生物的唾液蛋白有很大的差异，而且新的蛋白质家族经常在同一科的不同属中发现，甚至在亚属中也有发现。跳蚤与它们的脊椎动物宿主一起辐射进化，包括在 6500 万年前开始的哺乳动物扩张中。目前，只有一种跳蚤——印鼠客蚤（Xenopsylla cheopis）——通过唾液转录组分析来揭示唾液成分或唾液组。我们展示了猫蚤（Ctenocephaides felis）唾液组的分析结果。
从成年跳蚤的唾液腺 cDNA 文库中随机测序、组装和注释。猫蚤和鼠蚤的唾液组共有磷酸酶家族（失活）、CD-39 型脱氨酶、腺苷脱氨酶和酯酶。抗原 5 成员也是两种唾液组所共有的，防御素也是如此。FS-I/Cys7 和 8-Cys 肽家族也为两种跳蚤所共有，且为这些生物所特有。与 holotricin 相似的富含甘氨酸-组氨酸的肽只在猫蚤中发现，大量表达的无半胱氨酸肽和一种新的短肽家族也是如此。
结论/意义：与吸血的双翅目昆虫（蚊子、沙蝇和黑蝇）相比，跳蚤似乎将其唾液组的很大一部分集中在小多肽中，这些多肽没有已知的功能，但可能作为止血或炎症的抑制剂。它们还在一个磷酸酶家族的扩张中独一无二，该家族似乎缺乏酶活性，其功能未知。
