1.3.1.33 evolution all modern sequences of light-dependent protochlorophyllide oxidoreductase POR diverged from a single sequence about 1.36 billlion years ago. The LPOR gene was then duplicated at least 10 times in angiosperms, leading to the formation of two or even more LPOR isoforms in multiple species. In the case of Arabidopsis thaliana, isoforms PORA and PORB originated in one duplication event, in contrary to the isoform PORC, which diverged first 762710 1.3.1.33 evolution DPOR (EC 1.3.7.7) and LPOR (EC 1.3.1.33) initially evolved in the ancestral prokaryotic genome perhaps at different times. DPOR originated in the anoxygenic environment of the Earth from nitrogenase-like enzyme of methanogenic archaea. Due to the transition from anoxygenic to oxygenic photosynthesis in the prokaryote, the DPOR was mostly inactivated in the daytime by photosynthetic O2 leading to the evolution of oxygen-insensitive LPOR that could function in the light. The primary endosymbiotic event transferred the DPOR and LPOR genes to the eukaryotic phototroph, the DPOR remained in the genome of the ancestor that turned into the plastid, whereas LPOR was transferred to the host nuclear genome. Despite the evolution of its nonhomologous isofunctional counterpart LPOR, the DPOR continues to be functional in both oxygenic and anoxygenic photosynthetic organisms. Thus, DPOR was not exactly replaced but supplemented with the LPOR. Limnohabitans sp. strain 15K has acquired LPOR through horizontal gene transfer 763678 1.3.1.33 evolution DPOR (EC 1.3.7.7) and LPOR (EC 1.3.1.33) initially evolved in the ancestral prokaryotic genome perhaps at different times. DPOR originated in the anoxygenic environment of the Earth from nitrogenase-like enzyme of methanogenic archaea. Due to the transition from anoxygenic to oxygenic photosynthesis in the prokaryote, the DPOR was mostly inactivated in the daytime by photosynthetic O2 leading to the evolution of oxygen-insensitive LPOR that could function in the light. The primary endosymbiotic event transferred the DPOR and LPOR genes to the eukaryotic phototroph, the DPOR remained in the genome of the ancestor that turned into the plastid, whereas LPOR was transferred to the host nuclear genome. Despite the evolution of its nonhomologous isofunctional counterpart LPOR, the DPOR continues to be functional in both oxygenic and anoxygenic photosynthetic organisms. Thus, DPOR was not exactly replaced but supplemented with the LPOR. LPOR protein phylogeny further corroborates the horizontal gene transfer from cyanobacteria -, 763678 1.3.1.33 evolution oxygen-sensitive dark-operative NADPH:Pchlide oxidoreductase enzyme (DPOR) and light-dependent NADPH:protochlorophyllide oxidoreductase (LPOR) show very low sequence homology. In most organisms they occur simultaneously. However, angiosperms lack LPOR and became unable to synthesize chlorophyllides and chlorophylls (Chls) in the absence of light 763100 1.3.1.33 malfunction a PORA null mutant (porA-1) and PORA RNAi lines display severe photoautotrophic growth defects, which can be partially rescued on sucrose-supplemented growth media. Elimination of PORA during skotomorphogenesis results in reductions in the volume and frequency of prolamellar bodies, and in photoactive Pchlide conversion 726185 1.3.1.33 malfunction an enzyme-less mutant grows photoautotrophically in moderate light and contains a maximum of 20% of the wild type chlorophyll level 726255 1.3.1.33 malfunction it is shown that a porA-1 null mutant (porA mutant) carries a second dissociation insertion in another gene closely linked to the PORA gene that is expected to affect the phenotype of the porA mutant 726188 1.3.1.33 malfunction it is shown that an Arabidopsis thaliana porB-1 porC-1 double mutant can be functionally rescued by the addition of ectopically expressed PORA, which suffices in the absence of either PORB or PORC to direct bulk chlorophyll synthesis and normal plant development 726185 1.3.1.33 malfunction map-based cloning of the faded green leaf (fgl) locus in Oryza sativa is performed, and reveals that fgl harbors a 1-bp deletion in the coding region of OsPORB, resulting in a frameshift mutation and premature translational termination. Mutant is complemented by OsPORB 726175 1.3.1.33 malfunction overexpression of PORC in Arabidopsis thaliana reduces the accumulation of protochlorophyllide in high light-grown plants that results in minimal generation of 1O2 and plants are protected from 1O2-mediated oxidative damage caused by high light. PORC overexpression protects the plants from oxidative herbicidal action of 5-aminolevulinicacid. Overexpression of PORC results in coordinated upregulation of gene/protein expression of several Chl biosynthetic pathway enzymes resulting in enhanced Chl synthesis in light-grown plants 726283 1.3.1.33 malfunction RNAi based simultaneous silencing of all forms of light-dependent NADPH:protochlorophyllide oxidoreductase genes results in the accumulation of protochlorophyllide in tobacco 741187 1.3.1.33 metabolism ferredoxin-dependent biliverdin reductase, PCYA1 (EC 1.3.7.5), is a key enzyme involved in the biosynthesis of bilins, mechanism of bilin-mediated regulation of chlorophyll biosynthesis, and regulatory mechanisms of tetrapyrrole biosynthesis in Chlamydomonas reinhardtii, overview. Chlamydomonas PCYA1 uniquely interacts with light-dependent protochlorophyllide oxidoreductase LPOR (protochlorophyllide reductase, EC 1.3.1.33) via its FDBR domain, but not with ferredoxin:protochlorophyllide reductase DPOR (EC 1.3.7.7). This interaction is specific to Chlamydomonas since the Arabidopsis thaliana homologous proteins do not interact with each other, yeast two-hybrid and pull down assay analyses of protein-protein interaction -, 763107 1.3.1.33 metabolism the enzyme allows for the rapid formation of chlorophyll after illumination while avoiding photodamage. The formation of protochlorophyllide-enzyme(LPOR) complexes is an initial step of etioplast development. the formation of pigment-LPOR complexes in prolamellar bodies is essential for the rapid and safe conversion of etioplasts to chloroplasts during the dark-to-light transition 758042 1.3.1.33 metabolism the nonhomologous enzymes, the light-independent protochlorophyllide reductase (DPOR, EC 1.3.7.7) and the light-dependent protochlorophyllide oxidoreductase (LPOR), catalyze the reduction of protochlorophyllide (Pchlide) to chlorophyllide (Chlide) in the penultimate step of biosynthesis of chlorophyll (Chl) required for photosynthetic light absorption and energy conversion. The two enzymes differ with respect to the requirement of light for catalysis and oxygen sensitivity. Stereospecific reduction of the D ring of Pchlide (protochlorophyllide) to Chlide (chlorophyllide) catalyzed by light-independent protochlorophyllide a reductase (DPOR) occurs in anoxygenic phototrophs and photosynthetic eukaryotes except most gnetophytes and all angiosperms. The reduction of the D ring Pchlide to Chlide is brought about by light-dependent protochlorophyllide oxidoreductase (LPOR) in light in oxygenic phototrophs. The reduction of Chlide a to Bchlide a in anoxygenic phototrophs is catalyzed by the stereospecific reduction of ring B by chlorophyllide a oxidoreductase (COR, EC 1.3.7.15). Both MV Pchlide and DV Pchlide are phototransformed to MV Chlide a and DV Chlide a, respectively, by light-dependent Pchlide oxidoreductase (LPOR) in oxygenic phototrophs. In the absence of light, anoxygenic photosynthetic bacteria and oxygen evolving phototrophs catalyze Pchlide reduction by the light-independent Pchlide oxidoreductase (DPOR). The DV Chlide a is immediately converted to MV Chlide a by DV reductase -, 763678 1.3.1.33 additional information a clear distinction of the DPOR and LPOR functions cannot be made as oxygen-sensitive DPOR, which is typically inactivated in the increased oxygen concentration, remains functional in Dinoroseobacter shibae. The TFT motif fragment from LPOR and BchL/ChlL is found to be absent from other SDR proteins and has no similarity with the Fe protein of nitrogenase NifH. The TFT motif is previously found to be present between the NAA motif,which is one of the NADPH binding sites, and the catalytic YxxxK motif. The mutation of conserved residues in TFT motif results in complete inhibition of the LPOR activity -, 763678 1.3.1.33 additional information the TFT motif fragment from LPOR and BchL/ChlL is found to be absent from other SDR proteins and has no similarity with the Fe protein of nitrogenase NifH. The TFT motif is previously found to be present between the NAA motif, which is one of the NADPH binding sites, and the catalytic YxxxK motif. The mutation of conserved residues in TFT motif results in complete inhibition of the LPOR activity 763678 1.3.1.33 additional information the TFT motif fragment from LPOR and BchL/ChlL is found to be absent from other SDR proteins and has no similarity with the Fe protein of nitrogenase NifH. The TFT motif is previously found to be present between the NAA motif,which is one of the NADPH binding sites, and the catalytic YxxxK motif. The mutation of conserved residues in TFT motif results in complete inhibition of the LPOR activity 763678 1.3.1.33 physiological function in leaf of etiolated seedlings, prolamellar bodies are smaller in the etioplasts of mutant plants than in the wild type. In field-grown seedlings, the chloroplasts in the light-green sectors of mutant leaves exhibit decreased thylakoid stacking with a few plastglobules. PorB is essential for both prolamellar bodies and photoactive protochlorophyllide formation in dark conditions for light-dependent chlorophyll synthesis 743467 1.3.1.33 physiological function isoform POR1 supports photoacclimation, whereas isoform POR2 is responsible for daily chlorophyll synthesis 741255 1.3.1.33 physiological function key enzyme of chlorophyll biosynthesis in angiosperms. Photoenzyme, which catalyzes the light-activated trans-reduction of the C17-C18 double bond of the porphyrin ring of protochlorophyllides. Due to the light requirement, dark-grown angiosperms cannot synthesize chlorophyll 763675 1.3.1.33 physiological function LHPP (light-harvesting POR:Pchlide complexes) assembly is indispensable for barley POR functions and seedling greening 725793 1.3.1.33 physiological function light-dependent protochlorophyllide oxidoreductase (LPOR) is a rate-limiting key chlorophyll biosynthetic enzyme -, 763107 1.3.1.33 physiological function light-dependent reaction of chlorophyll biosynthesis. The enzyme (POR) is also important in plant development as it is the main constituent of prolamellar bodies in etioplast membranes 763023 1.3.1.33 physiological function low levels of isoform PorA are sufficient for leaf greening in rice, even in the absence of isoform PorB activity 743467 1.3.1.33 physiological function OsPORA mainly functions in the early stages of leaf development 726175 1.3.1.33 physiological function OsPORB is essential for maintaining light-dependent chlorophyll synthesis throughout leaf development, especially under high-light conditions 726175 1.3.1.33 physiological function the enzyme (LPOR) exhibits an intrinsic ability to form prolamellar body-like ultrastructures in the presence of the co-accumulation of protochlorophyllide. However, the prolamellar body-like structure differs from the authentic prolamellar bodies regarding NADPH deficiency -, 763334 1.3.1.33 physiological function the enzyme is essential for chlorophyll synthesis 741396 1.3.1.33 physiological function the reduction of protochlorophyllide (Pchlide) to chlorophyllide (Chlide) a is of crucial importance in the chlorophyll biosynthetic pathway as this step regulates the synthesis of Chl by feedback control. Pchlide reduction takes place by two nonhomologous enzymes DPOR and LPOR which differ with respect to their requirement of light. LPOR evolved in an independent evolutionary event immediately after the GOE on earth. However, unlike DPOR, LPOR uses NADPH as the reductant for the reduction of the double bond of Pchlide in the presence of light and is insensitive to oxygen attack. Due to the functional convergence, the two Pchlide reducing enzymes may be referred as nonhomologous isofunctional enzymes, mechanism of reduction of Pchlide to Chlide in the absence or presence of light by DPOR or LPOR -, 763678