蝦白點症病毒感染後草蝦基因表現之分析

Abstract

由白點症病毒（white spot syndrome virus; WSSV）感染所引起的養殖蝦急性感染症－蝦類白點症（white spot syndrome; WSS），是近十年來影響蝦類養殖業最嚴重的重要疾病。雖然目前已對白點症病毒的研究陸續獲致不少的成果，但至今對此病卻尚無一套確切有效的治療策略與方法。因此在本研究中，從寄主的防禦機制切入，藉由分析數個草蝦基因的轉錄表現探討其受白點症病毒感染之影響，並進而推測其可能作用的機制。本研究中，共探討了19個草蝦防禦相關基因，其中2個基因是經由本研究選殖所得。經過分類整理後，以WSSV感染草蝦為模式，利用反轉錄?－聚合?鏈反應（RT-PCR）分析數個基因在不同病毒感染時序轉錄表現。依據其表現型態及該分子參與的反應路徑，推測出有數個可能與白點症病毒感染後與寄主防禦機制相關且部分基因則與病毒感染後之時序而呈現表現量的變化，其中原酚氧化?活化系統及JAK/STAT訊息傳遞路徑有被病毒感染而誘發其活性以對抗病毒感染，而凝血機制及抗菌勝?形成的防禦機制反而因病毒感染而抑制。此外，藉由分析在本研究中選殖到的草蝦STAT分子完整cDNA序列及草蝦Pacifastin-related precusor部分cDNA序列發現前者在演化上具有高度保守性。 由本研究結果所提供的基礎資訊，期望有助於加速找出或擬訂出抗白點症病毒的策略。

Penaeus monodon is a host species to white spot syndrome (WSS), a serious disease that has impacted the shrimp farming industry all over the world. The present study investigates P. monodon's defense mechanisms against the causative pathogen, the large, double-stranded, white spot syndrome virus (WSSV). Temporal analysis of 19 genes that are related to biodefense was performed in WSSV-infected P monodon by RT-PCR, and results suggested several defense mechanisms that may respond to WSSV infection, including the prophenoloxidase activating system and the JAK/STAT signal transduction pathway. On the other hand, the clotting system and expression of antimicrobial peptide genes seem to be inhibited by WSSV infection. Of these 19 genes, two genes that code for the signal transducer and activator of transcription (STAT) and pacifastin-related precursor of P. monodon were first reported in this study. Thus, the P. monodon cDNAs of these two genes were subsequently cloned. The full-length cDNA sequences of STAT and the partial cDNA sequences of pacifastin-related precursor were determined. The cDNA for PmSTAT is 2322 bases in length and its coding region encodes a polypeptide of 744 amino acids. Comparison with the STAT from many other species suggests that evolutionarily, PmSTAT is highly conserved. Analysis of the deduced amino acid sequence of PmPP, a predicted proteinase inhibitor precursor, indicates it contains 9 or more proteinase inhibitors domains: 7 pacifastin light-chain proteinase inhibitor domains and at least 2 kunitz-type serine proteinase inhibitor domains.