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|標題:||Effects of juvenile hormone (JH) on the glutathione S-transferase (GST) in the fat body of Spodoptera litura larvae
麩胱甘肽硫轉基酶(glutathione S-transferase, GST)為一多功能酵素，主要扮演代謝角色，另外亦擁有攜帶蛋白功能。於先前研究中，發現斜紋夜蛾(Spodoptera litura)脂肪體內GST活性會於第六齡第0日齡處理青春激素類似物(juvenile hormone analog, JHA)後逐漸上升。本研究進一步發現此誘導活性，亦可發生於JH-Ⅲ之處理；並由轉錄和轉譯抑制劑處理，顯示此誘導活性乃經由基因層次所引發。隨後藉由麩胱甘肽親和性膠體管柱層析法(GSH-agarose affinity chromatography)，分離得斜紋夜蛾脂肪體內GST群，發現其中兩群明顯受JHA誘導；選擇其中一受JHA誘導之GST，進行蛋白質N端定序，得一16個胺基酸序列。另外，藉由之前所製作減除雜合基因庫(subtractive cDNA library)中，所獲得部分GST基因片段，求得一全長具784 bp之cDNA，命名為SlGST1(accession number is AY506545)，其蛋白質序列前16個胺基酸完全符合先前所得蛋白質N端定序之序列，因此認為所純化得到之GST即為SlGST1。利用SlGST1 cDNA為探針(probe)，進行北方墨點法，顯示此基因於第六齡第0、1和2日齡皆可受JHA誘導。最後利用人類(Homo sapiens)、黃果蠅(Drosophila melanogaster)、剛比亞瘧蚊(Anopheles gambiae)和數種鱗翅目所發表之GST序列進行歸群分析，發現所得之SlGST1乃歸屬於epsilon group，其為一群與抗藥性有關之GST。到底SlGST1於此具有何生理意義？目前仍無法下正確結論。僅臆測此誘導反應可能牽扯激素反應和毒理反應。
Glutathione S-transferases (GSTs) are a family of multi-functional enzymes that have roles on the functions of metabolism or as carrier proteins. Previous study has demonstrated that the fat body GST activity of Spodoptera litura larvae is able to be induced by juvenile hormone analog (JHA) treatments. In this continuous study, a similar result was observed by JH-Ⅲ treatments. Furthermore, the JH-dependent GST activation was controlled on its gene level based on the results of the treatments with transcriptional and translational inhibitor, respectively. Afterwards, GSTs were isolated from the fat body of S. litura larvae by GSH-agarose affinity chromatography, and two groups of JHA-induced GSTs were observed. One of two groups of GSTs was selected to determine its N-terminal sequence, and it turned out 16 amino acids sequence to be obtained. On the other hand, a full-length cDNA with 784 bp was obtained, named SlGST1 (accession number is AY506545), which based on a partial sequence of GST from a subtractive cDNA library, and its first 16 amino acids of N-terminal sequence are consistent with the N-terminal sequence of the purified GST protein. Then SlGST1 was used as cDNA probe to detect its expression, resulting that SlGST1 was able to be induced by JHA in the fat bodies of sixth instar larvae. The sequence of alignment revealed the SlGST1 was classified into epsilon group, which has been implicated in conferring insecticide resistance. What is the physiological role of the SlGST1? It is unclear; however, I speculate that the inductive effect may be involved in response to both hormonal and toxicological stimulation.
|Appears in Collections:||昆蟲學系|
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