Aspergillus屬中的水平基因轉移及基因體中的GC變化

Abstract

水平基因轉移在原核生物及部分的真核生物演化中扮演重要的角色，不同於一般有性的遺傳物質轉移，水平基因轉移是一個遺傳物質轉移至不同物種的過程，在原核生物中，水平基因轉移事件發生頻繁且原核生物常經由此過程增加對於環境的適應力，最廣為被人提及的病人產生抗藥性的事件就是屬於基因轉移發生的案例。在現在這個基因體大量被解碼的時代中，水平基因轉移事件逐漸被發現，水平基因轉移的發生可以解釋一些物種所產生的新特徵或人類、動物及植物上的新疾病。搜尋潛在轉移基因有許多方法，例如找出不同於整個基因體特色的片段或是發現序列度異於認知中的演化關係，因為許多因素會影響水平基因轉移事件的判斷，應該利用不同方法及數據來驗證水平基因轉移的案例。在此研究中，發現一個從真菌轉移至Stigmatella aurantiaca (屬於黏液菌myxobacteria中的一種土壤細菌)的水平基因轉移案例，從演化關係及基因體特徵分析中推論Aspergillus clavatus中的同源基因與水平轉移的基因STAUR_2131最相近，但確切的序列來源尚不清楚。

Horizontal Gene Transfer (HGT), also called Lateral Gene Transfer (LGT), plays an important role in evolution of prokaryotes and part of eukaryotes. HGT is the nonsexual process of genetic material transfer across species. It is well known that HGT events occur frequently among prokaryotes that can often increase fitness to colonize new environment. The common transfer events that people often mentioned is developing drug resistance. However, as genome sequencing era coming, HGTs found in eukaryotes increasingly. HGT events may explain some new traits of organisms and even new disease to human, animals and plants. There are several approaches, which based on genome-wide features, sequence similarity and phylogeny incongruence, can screen out potential HGT cases. Since, there are different possibilities that can contribute to the gene anomalies, HGTs should be confirmed by different approaches, especially phylogeny analysis. In this study, I find one HGT event, transferred from fungi to Stigmatella aurantiaca. From the analysis of phylogeny and genome characteristics, the orthologous gene of Aspergillus clavatus is the most closed gene sequence to the HGT gene, STAUR_2131, but where the sequence come from is unknown.