甘藷基因ipomoelin之選殖與表現

Cloning and Expression of the Ipomoelin Gene from Sweet Potato

由相減式雜和反應所得到之甘藷傷害誘導表現基因已知可受甲基化茉莉酸（methyl jasmonic acid）所誘導，但卻不受離層酸（ABA）所影響，在之前的試驗中所得之ipomoelin基因的表現受水楊酸（salicylic acid）所抑制，並與蛋白質激酶及磷酸酶相關。在本研究中由甘藷基因庫中篩選到ipomoelin基因的全長，並且其蛋白質序列與其他蛋白質序列的比對發現，ipomoelin與外源凝集素（lectin）具有高度相似性。為了更進一步研究Ipomoelin基因的功能，將ipomoelin基因構築到細菌的表現系統，並由1 mM IPTG誘導大腸桿菌大量表現ipomoelin蛋白質。本文結果發現ipomoelin蛋白質可在IPTG誘導一小時後開始表現，並且在四小時的誘導後可達到最高量表現，而由此大腸桿菌系統表現出來的ipomoelin蛋白質的品質及產量均適宜於更進一步的功能探討研究。

A full-length cDNA encoding ipomoelin protein was isolated from an enriched cDNA library, which contained wound-inducible cDNAs subtracted from that of unwounded sweet potato. Ipomoelin gene can be induced by methyl jasmonic acid, but independent of ABA. In prior studies, the expression of ipomoelin gene was found to be inhibited by salicylic acid, and related to protein kination and phosphorylation. In this study, the deduced protein sequence of ipomoelin was compared with amino acid sequences of other proteins, and it exhibited a high homology with lectin. In order to study further the function of ipomoelin, the ipomoelin gene was constructed and transformed into a bacteria expression system. The result shows that the ipomoelin protein could be over-expressed in E. coli one hour after IPTG induction and reached a maximum four hours after induction.