Protochlorophyllide Reduction And Greening

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Protochlorophyllide Reduction And Greening

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Author : C. Sironval
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06

Protochlorophyllide Reduction And Greening written by C. Sironval and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Science categories.

Proceedings of a Meeting held at the University of Liège, Belgium, 8-9 August 1983

Photoreduction Of Protochlorophyllide A To Chlorophyllide A During The Biogenesis Of The Photosynthetic Apparatus In Highter Plants

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Author : Benoit Schoefs
language : en
Publisher: Universal-Publishers
Release Date : 2000-08

Photoreduction Of Protochlorophyllide A To Chlorophyllide A During The Biogenesis Of The Photosynthetic Apparatus In Highter Plants written by Benoit Schoefs and has been published by Universal-Publishers this book supported file pdf, txt, epub, kindle and other format this book has been release on 2000-08 with Nature categories.

This thesis is divided into 4 chapters summarizing this contribution on selected topics related to chlorophyll biosynthesis and biogenesis of the photosynthetic apparatus. The first chapter deals with the state of Pchlide in nonilluminated leaves. The comparison of the photoactive Pchlide absorbance spectra throughout the development in the dark, reveals that the proportion of P638-645 and P650-657 is not much modified during this period. The Gaussian deconvolutions of 77 K fluorescence spectra of nonphotoactive and photoactive Pchlide indicated the presence of three and 5 spectral forms, respectively. None of the nonphotoactive Pchlide forms is accumulated during the dark-growth. In constrast, photoactive Pchlide P650-657 is particularly accumulated. In the second chapter, we describe the photoreduction of Pchlide to Chlide. We conclude that the mechanism of photoreduction is independent on the leaf developmental stage. Using 77 K fluorescence spectroscopy, the Chlide spectral forms corresponding to the three photoactive Pchlides were identified. In leaves with proplastids, C670-675 is mainly formed whereas in leaves with etioplasts C684-696 is produced. During the 1st hour of greening, the newly formed Chlide molecules are not protected by carotenoids. The evidence for the involvement of a photocycle involving two spectral forms of Chlide in protection of newly formed Chlide is presented. In the third chapter, a method for the isolation of photoactive Pchlide yielding complexes characterized by spectral properties similar to those found in intact leaves is described. In the fourth chapter, it is explained that the different fates of the first products of the photoreduction, described in the 2nd chapter, influence the greening process. In fact, C684-696 is only produced in small amounts in plants with proplastids. Therefore the increase of the photosynthetic activity of these leaves is delayed. Nevertheless, during the first 8 h of greening, a weak photosynthetic activity is detected in these leaves. Fluorescence measurements reveal that a large part of the Chl remains nonintegrated to the photosystems. In young leaves, rapid Chl integration into the photosynthetic units occurs when both carotenoids and Chl are massively synthesized.

The Photoreduction Of Protochlorophyllide And Greening

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Author : C. J. Walker
language : en
Publisher:
Release Date : 1987

The Photoreduction Of Protochlorophyllide And Greening written by C. J. Walker and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1987 with categories.

Genetic Analysis Of Protochlorophyllide Reduction In C Am Y Om O As E I A I I

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Author : Clark Fugier Ford
language : en
Publisher:
Release Date : 1981

Genetic Analysis Of Protochlorophyllide Reduction In C Am Y Om O As E I A I I written by Clark Fugier Ford and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1981 with Algae categories.

Nadph

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Author :
language : en
Publisher:
Release Date : 2013

Nadph written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.

The biosynthesis of chlorophyll is a critical biochemical step in the development of photosynthetic vascular plants and green algae. From photosynthetic bacteria (cyanobacteria) to algae, non-vascular plants, gymnosperms and vascular plants, mechanisms have evolved for protochlorophyllide reduction a key step in chlorophyll synthesis. Protochlorophyllide reduction is carried out by both a light-dependent (POR) and light-independent (LIPOR) mechanisms. NADPH: protochlorophyllide oxidoreductase (EC 1.3.1.33, abbreviated POR) catalyzes the light-dependent reduction of protochlorophyllide (PChlide) to chlorophyllide (Chlide). In contrast, a light-independent protochlorophyllide reductase (LIPOR) involves three plastid gene products (chlL, chlN, and chlB) and several nuclear factors. Our work focused on characterization of both the POR and LIPOR catalyzed processes.

Genetic Manipulation Of Nadph Protochlorophyllide Oxidoreductase Content In Arabidopsis Reveals Essential Roles In Prolamellar Body Formation And Plant Development

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Author : Troy N. Paddock
language : en
Publisher:
Release Date : 2008

Genetic Manipulation Of Nadph Protochlorophyllide Oxidoreductase Content In Arabidopsis Reveals Essential Roles In Prolamellar Body Formation And Plant Development written by Troy N. Paddock and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with Angiosperms categories.

Abstract: Chlorophyll synthesis in angiosperms requires light because, in contrast to other photosynthetic organisms, they rely exclusively on a light-dependent mechanism to reduce protochlorophyllide during chlorophyll biosynthesis. NADPH:protochlorophyllide oxidoreductase (POR) catalyses a light-dependent reduction of protochlorophyllide to chlorophyllide, which is subsequently transformed to chlorophyll. In etioplasts during skotomorphogenesis, POR forms a photolabile aggregate of NADPH-POR-Pchlide localized to the prolamellar bodies. In Arabidopsis there is a three-member gene family encoding structurally related but differentially regulated POR enzymes denoted PORA, PORB and PORC. PORA and PORB accumulate during skotomorphogenesis. PORB and PORC accumulate during seedling development and throughout the life of the plant, during which they are responsible for bulk chlorophyll synthesis. Here I describe the detailed molecular-genetic dissection of the functions of the different POR isoforms. While single porB-1 or porC-1 null mutants display no distinct light-grown phenotypes, the porB-1 porC-1 double mutant displays a severe xantha (highly chlorophyll-deficient) phenotype. In response to illumination, chlorophyll production, thylakoid stacking and photomorphogenesis are restored in the PORA-overexpressing porB-1 porC-1 transgenic lines. Therefore, the porB-1 porC-1 double mutant is functionally rescued by ectopically expressed PORA, which suffices in the absence of either PORB or PORC to direct bulk chlorophyll synthesis and normal plant development. Using reverse genetic approaches, our lab identified a porA-1 null mutant which I have characterized here; additionally I have characterized PORA RNAi knockdown lines. The porA-1 and PORA RNAi lines display photoautotrophic growth blocks which are partially rescued on sucrose-supplemented media. porA-1 mutant seedlings display defects in etioplast development with reductions in prolamellar body accumulation and photoactive Pchlide conversion. Further analysis of the porB-1 porC-1 double null mutant reveals independent PORA catalytic activity in the cauline leaves of low-light grown plants. The porA-1 porB-1 and porA-1 porC-1 double mutants were used investigate the contributions of each POR individual isoform to Chl biosynthesis and growth in green plants. The porA-1 porB-1 and porA-1 porC-1 mutants have photoautotrophic growth defects which resemble that of the porA-1 single mutant. In addition, etioplast development in the porA-1 porB-1 double mutant is defective, with no detected prolamellar body formation or photoactive protochlorophyllide conversion.

A Comparative Study Of Protochlorophyllide Spectral Forms During Development And Greening Of Four Varieties Of Dark Grown Plants

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Author : Mohammad Reza Amirjani
language : en
Publisher:
Release Date : 2004

A Comparative Study Of Protochlorophyllide Spectral Forms During Development And Greening Of Four Varieties Of Dark Grown Plants written by Mohammad Reza Amirjani and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with categories.

Recent Advances In Biological Membrane Studies

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Author : Lester Packer
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06

Recent Advances In Biological Membrane Studies written by Lester Packer and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Science categories.

A NATO Advanced Study Institute on "New Developments and Methods in Membrane Research and Biological Energy Transduction" was held in order to consider some of the most recent developments in membrane research methodologies and results, with particular emphasis on studies of biological energy transduction. The partic ipants in the Institute dealt with three general areas of membrane study: membrane structure (with emphasis on lipid and protein components), membrane component assembly (with particular emphasis on mitochondria and chloroplasts), and the specialized functions of certain membrane systems. This last area included discussions of topics such as drug transformation, the role of membrane electron transport in the generation of oxygen radicals, the effect of oxygen radicals on cellular homeostasis and on the structure, organization and function of the acetylcholine receptor. Lectures and posters were concerned with two central questions: what is the function of membrane structure in energy transduction and how can energy trans duction be effectively measured and assessed? This text presents the content of the major lectures and important posters presented during the Institute's program. In issuing this book, the editor hopes to convey the proceedings of the Institute to a larger audi ence and to offer a comprehensive account of those developments in membrane research that were considered on the Island of Spetsai between August 16 and August 29, 1984. L. Packer Berkeley, California February 1985 v CONTENTS I. STRUCTURE AND BIOGENSIS Membrane Structure: Neutron Diffraction and Small Angle Scattering Studies •••••••••• 1 G.

Nadph Protochlorophyllide Oxidoreductase Por

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Author : Alessio Garrone
language : en
Publisher:
Release Date : 2017

Nadph Protochlorophyllide Oxidoreductase Por written by Alessio Garrone and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.

NADPH:protochlorophyllide oxidoreductase (POR), EC 1.3.1.33, is a key enzyme in the biosynthesis of chlorophyll in all organisms with oxygenic photosynthesis. POR catalyzes the reduction of protochlorophyllide (PChlide) to chlorophyllide (Chlide) by the absorption of light in the presence of the cofactor NADPH. In plants, two different isoenzymes are found, POR A and POR B. POR A is transiently active in etiolated plant seedlings, whereas POR is predominantly active throughout the greening process and in greened and adult plants. The two plant POR isoenzymes are compared with respect to their catalytic efficiency and their reaction mechanism in experiments using highly purified recombinant POR from barley (Hordeum vulgare L.). POR B shows a 6-fold higher catalytic efficiency (kcat/KM) but the same reaction mechanism when compared with POR A. The increased catalytic efficiency is attributed to a higher substrate binding affinity and a higher conformational flexibility of protein sites in the surrounding of the active centre. With the aim of gaining a deeper insight into the active-site architecture a 3-D model is predicted for POR B by using in silico homology modelling techniques. The prediction identifies His-138, Ser-164, Lys-216 and Tyr-299 as important residues for the correct positioning of the PChlide substrate within the active site. Moreover, the active site Tyr-212 and Lys-216 also play a key role in PChlide binding whereas Tyr-212 is also shown to take part in the proton transfer to the C(18) position of PChlide. The remaining residues within the catalytic motif, Lys-213, Asp214 and Ser-215 obviously create a polar interaction site, which is finely tuned by the cooperation of all three residues to facilitate the proper alignment of PChlide within the active site and to support a highly efficient photochemistry. Only small steric perturbations or changes in the hydrogen bonding tendency of these residues affect the photoreaction dramatically.

The Nuclear Y Genes And The Light Independent Reduction Of Protochlorophyllide In Chalmydomonas Reinhardtii

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Author : Julie Rochelle Jageman
language : en
Publisher:
Release Date : 2003

The Nuclear Y Genes And The Light Independent Reduction Of Protochlorophyllide In Chalmydomonas Reinhardtii written by Julie Rochelle Jageman and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with categories.