Heme biosynthesis is essential for almost all living organisms. Despite its conserved function, the pathway's enzymes can be located in a remarkable diversity of cellular compartments in different organisms. This location does not always reflect their evolutionary origins, as might be expected from the history of their acquisition through endosymbiosis. Instead, the final subcellular localization of the enzyme reflects multiple factors, including evolutionary origin, demand for the product, availability of the substrate, and mechanism of pathway regulation. The biosynthesis of heme in the apicomonad Chromera velia follows a chimeric pathway combining heme elements from the ancient algal symbiont and the host. Computational analyses using different algorithms predict complex targeting patterns, placing enzymes in the mitochondrion, plastid, endoplasmic reticulum, or the cytoplasm. We employed heterologous reporter gene expression in the apicomplexan parasite Toxoplasma gondii and the diatom Phaeodactylum tricornutum to experimentally test these predictions. 5-aminolevulinate synthase was located in the mitochondria in both transfection systems. In T. gondii, the two 5-aminolevulinate dehydratases were located in the cytosol, uroporphyrinogen synthase in the mitochondrion, and the two ferrochelatases in the plastid. In P. tricornutum, all remaining enzymes, from ALA-dehydratase to ferrochelatase, were placed either in the endoplasmic reticulum or in the periplastidial space.

• Klíčová slova
• Chromera velia, heterologous expression, predictions, tetrapyrrole biosynthesis,
• MeSH
• Alveolata fyziologie   MeSH
• Apicomplexa metabolismus   MeSH
• biologický transport MeSH
• hem metabolismus   MeSH
• metabolické sítě a dráhy * MeSH
• mitochondrie genetika   metabolismus   ultrastruktura   MeSH
• molekulární evoluce MeSH
• protozoální proteiny chemie   genetika   metabolismus   MeSH
• regulace genové exprese enzymů MeSH
• rozsivky metabolismus   MeSH
• sekvence aminokyselin MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• hem MeSH
• protozoální proteiny MeSH

Fatty acids are essential components of biological membranes, important for the maintenance of cellular structures, especially in organisms with complex life cycles like protozoan parasites. Apicomplexans are obligate parasites responsible for various deadly diseases of humans and livestock. We analyzed the fatty acids produced by the closest phototrophic relatives of parasitic apicomplexans, the chromerids Chromera velia and Vitrella brassicaformis, and investigated the genes coding for enzymes involved in fatty acids biosynthesis in chromerids, in comparison to their parasitic relatives. Based on evidence from genomic and metabolomic data, we propose a model of fatty acid synthesis in chromerids: the plastid-localized FAS-II pathway is responsible for the de novo synthesis of fatty acids reaching the maximum length of 18 carbon units. Short saturated fatty acids (C14:0-C18:0) originate from the plastid are then elongated and desaturated in the cytosol and the endoplasmic reticulum. We identified giant FAS I-like multi-modular enzymes in both chromerids, which seem to be involved in polyketide synthesis and fatty acid elongation. This full-scale description of the biosynthesis of fatty acids and their derivatives provides important insights into the reductive evolutionary transition of a phototropic algal ancestor to obligate parasites.

• Klíčová slova
• Chromera velia, Vitrella brassicaformis, de novo biosynthesis, desaturation, elongation, evolution, fatty acids,
• MeSH
• Apicomplexa klasifikace   genetika   metabolismus   MeSH
• biosyntetické dráhy genetika   MeSH
• desaturasy mastných kyselin klasifikace   genetika   metabolismus   MeSH
• druhová specificita MeSH
• elongasy mastných kyselin klasifikace   genetika   metabolismus   MeSH
• fylogeneze MeSH
• lidé MeSH
• mastné kyseliny biosyntéza   MeSH
• molekulární evoluce MeSH
• protozoální infekce parazitologie   MeSH
• protozoální proteiny klasifikace   genetika   metabolismus   MeSH
• synthasa mastných kyselin, typ 2 klasifikace   genetika   metabolismus   MeSH
• synthasa mastných kyselin, typ I klasifikace   genetika   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• desaturasy mastných kyselin MeSH
• elongasy mastných kyselin MeSH
• mastné kyseliny MeSH
• protozoální proteiny MeSH
• synthasa mastných kyselin, typ 2 MeSH
• synthasa mastných kyselin, typ I MeSH

Most photosynthetic eukaryotes synthesize both heme and chlorophyll via a common tetrapyrrole biosynthetic pathway starting from glutamate. This pathway was derived mainly from cyanobacterial predecessor of the plastid and differs from the heme synthesis of the plastid-lacking eukaryotes. Here, we show that the coral-associated alveolate Chromera velia, the closest known photosynthetic relative to Apicomplexa, possesses a tetrapyrrole pathway that is homologous to the unusual pathway of apicomplexan parasites. We also demonstrate that, unlike other eukaryotic phototrophs, Chromera synthesizes chlorophyll from glycine and succinyl-CoA rather than glutamate. Our data shed light on the evolution of the heme biosynthesis in parasitic Apicomplexa and photosynthesis-related biochemical processes in their ancestors.

• MeSH
• acylkoenzym A metabolismus   MeSH
• Alveolata metabolismus   MeSH
• chlorofyl biosyntéza   MeSH
• fotosyntéza * MeSH
• fylogeneze MeSH
• glycin metabolismus   MeSH
• molekulární sekvence - údaje MeSH
• protozoální DNA genetika   MeSH
• sekvenční analýza DNA MeSH
• tetrapyrroly biosyntéza   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• acylkoenzym A MeSH
• chlorofyl MeSH
• glycin MeSH
• protozoální DNA MeSH
• succinyl-coenzyme A MeSH Prohlížeč
• tetrapyrroly MeSH

Tryptophan is an essential amino acid that, in eukaryotes, is synthesized either in the plastids of photoautotrophs or in the cytosol of fungi and oomycetes. Here we present an in silico analysis of the tryptophan biosynthetic pathway in stramenopiles, based on analysis of the genomes of the oomycetes Phytophthora sojae and P. ramorum and the diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum. Although the complete pathway is putatively located in the complex chloroplast of diatoms, only one of the involved enzymes, indole-3-glycerol phosphate synthase (InGPS), displays a possible cyanobacterial origin. On the other hand, in P. tricornutum this gene is fused with the cyanobacteria-derived hypothetical protein COG4398. Anthranilate synthase is also fused in diatoms. This fusion gene is almost certainly of bacterial origin, although the particular source of the gene cannot be resolved. All other diatom enzymes originate from the nucleus of the primary host (red alga) or secondary host (ancestor of chromalveolates). The entire pathway is of eukaryotic origin and cytosolic localization in oomycetes; however, one of the enzymes, anthranilate phosphoribosyl transferase, was likely transferred to the oomycete nucleus from the red algal nucleus during secondary endosymbiosis. This suggests possible retention of the complex plastid in the ancestor of stramenopiles and later loss of this organelle in oomycetes.

• MeSH
• aldoso-ketosoisomerasy genetika   metabolismus   MeSH
• anthranilátfosforibosyltransferasa genetika   metabolismus   MeSH
• anthranilátsynthasa genetika   metabolismus   MeSH
• chloroplasty metabolismus   MeSH
• fylogeneze MeSH
• indol-3-glycerolfosfátsynthasa genetika   metabolismus   MeSH
• molekulární evoluce MeSH
• molekulární sekvence - údaje MeSH
• molekulární struktura MeSH
• Phytophthora metabolismus   MeSH
• rozsivky cytologie   genetika   metabolismus   MeSH
• sekvence aminokyselin MeSH
• tryptofan biosyntéza   chemie   MeSH
• tryptofansynthasa genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• aldoso-ketosoisomerasy MeSH
• anthranilátfosforibosyltransferasa MeSH
• anthranilátsynthasa MeSH
• indol-3-glycerolfosfátsynthasa MeSH
• phosphoribosylanthranilate isomerase MeSH Prohlížeč
• tryptofan MeSH
• tryptofansynthasa MeSH