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The Adaptive Evolution of Blood-feeding Ralated Multigene Families in Tick Saliva

Author: ZhangAiZuo
Tutor: HuangJingFei
School: University of Science and Technology of China
Course: Cell Biology
Keywords: Scapular Ixodes New features Basic trypsin inhibitor Evolution Serine protease inhibitors Vampire Ion channels
CLC: Q963
Type: Master's thesis
Year: 2011
Downloads: 57
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Abstract

There are a variety of gene families in the salivary glands of ticks, they play a key role in the process of ticks vampire. The study of the evolution of these multi-gene family not only be able to improve our understanding of the evolution of ticks and tick-class molecular mechanisms of adaptation vampire, so as to provide a reasonable idea to control ticks, but also be able to provide for us about the evolution of protein structure and function new cases. Kunitz / BPTI protein in large quantities in the salivary glands of ticks, by inhibiting the serine protease in the coagulation cascade reaction VIIa, Xa, thereby inhibiting the blood coagulation and platelet aggregation, and thus play an important role in the ticks bloodsucking process. This study system analysis the scapular Ixodes (Ixodes Scapularis) Kunitz / BPTI family evolution, expansion, gene expression, we found that depending on the cysteine ??pattern [CX (8) CX (15) CX (7) CX (12) CX (3) C, CX (8) CX (18) CX (5) CX (12) CX (3) C, CX (5,6) CX (15) CX (8) CX (11) CX (3) C] be divided into three groups (group Ⅰ, group Ⅱ, group III). Group Ⅰ widely distributed in various species of ticks, Kunitz / BPTI family ancestors state still has the classic function of inhibiting serine protease. Group Ⅱ and group Ⅲ, however, only in the hard tick genus (genus Ixodes), they Although the group Ⅰ evolution from, but the loss of the inhibiting serine protease motif subsequent functional site analysis and structure than on the discovery group Ⅱ evolution of the ion channel regulation the function of the motif. Phylogenetic analysis showed that the specific expansion of group Ⅱ and group Ⅲ Ixodes genus (genus Ixodes). Selection pressure analysis found that positive selection to drive the change of the group II and group Ⅲ-specific expansion and function. Finally, we summarized the evolution of the Kunitz / BPTI family in ticks Kunitz / BPTI protein oldest ticks should be with group Ⅰ immediate homologous. About 120 million years ago and 92 million years ago Argasidae Ixodidae separation Ixodidae a genome-wide replication after Ixodidae differentiation of former the groove type Prostriata and a Hougou Metastriata. Prostriata in gene level changes occur on the basis of the group Ⅰ produce two types of group Ⅱ and group Ⅲ insertions and deletions (indels) to differentiate into Ixodes are three types Kunitz / BPTI protein. The group Ⅰ in Metastriata the other types of genetic change. Expression Analysis found that the the group Ⅱ expansion in the Ixodes genus and group Ⅲ six genes (Isc.218, Isc.190, Isc.255, Isc.196, Isc.180, Isc.179) the vampire in the late expression was significantly upregulated (6-12 hours), these genes by regulating ion channels, thereby regulating the blood flow of the host's immune and blood-sucking point, resulting in Ixodes end of bloodsucking vampire efficiency, more conducive to the Ixodes long schedule vampire. In view of the functional importance of these genes and species-specific, and does not cause the host to produce its own immune, we suggest that these six genes are the target antigen as a vaccine design.

The Adaptive Evolution of Blood-feeding Ralated Multigene Families in Tick Saliva

Abstract

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