The tigA gene is a transcriptional fusion of glycolytic genes encoding triose-phosphate isomerase and glyceraldehyde-3-phosphate dehydrogenase in oomycota

Abstract

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.The enzymes triose-phosphate isomerase (TPI) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyze sequential steps in the major pathways of carbohydrate metabolism, including glycolysis and gluconeogenesis. GAPDH catalyzes the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate following its isomerization from dihydroxyacetone phosphate by TPI. In all organisms studied thus far, GAPDH is a tetrameric protein, which is homomeric (EC 1.2

Enzyme co-localization in pea leaf chloroplasts: glyceraldehyde-3-P dehydrogenase, triose-P isomerase, aldolase and sedoheptulose bisphosphatase

“…There is evidence from binding experiments (Stephan et al 1986) and from affinity electrophoresis experiments (Beeckmans et al 1990) for interaction between vertebrate triose-P isomerases and glyceraldehyde-3-P dehydrogenases, and in the diatom Phaeodactylum (Liaud et al 2000) and the non-photosynthetic oomycetes Achlya and Phytophthora (Unkles et al 1997) the two enzymes are present as a fusion protein.…”

Rewiring and regulation of cross-compartmentalized metabolism in protists

“…Another reported possibility of forming a complex that might allow metabolite channelling is the fusion of the successively acting enzymes triosephosphate isomerase (TPI) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as found in diatoms and oomycetes, unicellular eukaryotes belonging to the Stramenopiles (figure 1b) (Unkles et al 1997;Liaud et al 2000). Similarly, other combinations of glycolytic enzymes have occasionally been reported as fusion proteins: in the thermophilic eubacterium Thermotoga maritima phosphoglycerate kinase (PGK) and TPI are fused (Schurig et al 1995), and among eukaryotic microbes GAPDH and enolase are fused in the dinoflagellates Karina species and Heterocapsa triquetra (Takishita et al 2005).…”

“…The upper part, or ATP-investment phase, of glycolysis may occur in the cytosol or, alternatively, triosephosphates could be directly delivered from the chloroplasts to mitochondria (figure 1b), thus establishing a direct link between the Calvin cycle and mitochondrial metabolism (Liaud et al 2000). Importantly, optimized transfer of metabolites between chloroplasts and mitochondria is not without precedent: C. reinhardtii mitochondria penetrate into the chloroplast (Ehara et al 1995), and in malarial parasites the mitochondrion and apicoplast are closely associated and the enzymes required for haem biosynthesis partition across both compartments and the cytosol (Ralph et al 2004;Varadharajan et al 2004;van Dooren et al 2006).…”

Evolution of the coordinate regulation of glycolytic enzyme genes by hypoxia

“…Many functionally related bacterial genes are organized into physical operons that are regulated by a master operator element, usually positioned at the 5′ end of the operon, which regulates the transcriptional rate of all genes in the operon (Alefounder and Perham, 1989;Barnell et al, 1990;Hannaert et al, 2000;Liaud et al, 2000;Unkles et al, 1997). Evidence for glycolytic enzyme gene operons include linked pyruvate kinase and PFK genes in Clostridium acetobutylicum (Belouski et al, 1998); clustered genes for phosphoglycerate kinase (PGK), triosephosphate isomerase (TPI), phosphoglycerate mutase and enolase in Baccilus subtilis (Leyva-Vazquez and Setlow, 1994); linkage of GAPDH, PGK and TPI in Borrelia megaterium, Borrelia bungorferi and Borrelia hermsii (Gebbia et al, 1997;Schlapfer and Zuber, 1992); clustering of fructose 1,6-biphosphate aldolase, 3-phosphoglycerate kinase and GAPDH in E. coli (Alefounder and Perham 1989), and clustering of the glucose-6 dehydrogenase, 6-phosphogluconate dehydratase and glucokinase genes with a putative glucose transporter in Zymomonas mobilis (Barnell et al, 1990).…”