Unkles S E, Logsdon J M, Robison K, Kinghorn J R, Duncan J M
Scottish Crop Research Institute, Invergowrie, Dundee, United Kingdom.
J Bacteriol. 1997 Nov;179(21):6816-23. doi: 10.1128/jb.179.21.6816-6823.1997.
Genes encoding triose-phosphate isomerase (TPI) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) are fused and form a single transcriptional unit (tigA) in Phytophthora species, members of the order Pythiales in the phylum Oomycota. This is the first demonstration of glycolytic gene fusion in eukaryotes and the first case of a TPI-GAPDH fusion in any organism. The tigA gene from Phytophthora infestans has a typical Oomycota transcriptional start point consensus sequence and, in common with most Phytophthora genes, has no introns. Furthermore, Southern and PCR analyses suggest that the same organization exists in other closely related genera, such as Pythium, from the same order (Oomycota), as well as more distantly related genera, Saprolegnia and Achlya, in the order Saprolegniales. Evidence is provided that in P. infestans, there is at least one other discrete copy of a GAPDH-encoding gene but not of a TPI-encoding gene. Finally, a phylogenetic analysis of TPI does not place Phytophthora within the assemblage of crown eukaryotes and suggests TPI may not be particularly useful for resolving relationships among major eukaryotic groups.
编码磷酸丙糖异构酶(TPI)和甘油醛-3-磷酸脱氢酶(GAPDH)的基因在疫霉菌(卵菌门腐霉目中的成员)中融合,并形成一个单一的转录单元(tigA)。这是真核生物中糖酵解基因融合的首次证明,也是任何生物体中TPI-GAPDH融合的首例。致病疫霉的tigA基因具有典型的卵菌转录起始点共有序列,并且与大多数疫霉基因一样,没有内含子。此外,Southern杂交和PCR分析表明,在来自同一目(卵菌纲)的其他近缘属,如腐霉属,以及较远缘的水霉目属,如水霉属和绵霉属中,存在相同的基因组织。有证据表明,在致病疫霉中,至少还有一个编码GAPDH的基因的离散拷贝,但没有编码TPI的基因的离散拷贝。最后,TPI的系统发育分析并未将疫霉置于冠群真核生物组合中,这表明TPI可能对解析主要真核生物类群之间的关系不是特别有用。