Journal Article

Functional Analysis of Isoforms of NADPH:Protochlorophyllide Oxidoreductase (POR), PORB and PORC, in <i>Arabidopsis thaliana</i>

Tatsuru Masuda, Naoki Fusada, Naoki Oosawa, Ken’ichi Takamatsu, Yoshiharu Y. Yamamoto, Masaaki Ohto, Kenzo Nakamura, Koji Goto, Daisuke Shibata, Yumiko Shirano, Hiroaki Hayashi, Tomohiko Kato, Satoshi Tabata, Hiroshi Shimada, Hiroyuki Ohta and Ken-ichiro Takamiya

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 10, pages 963-974
Published in print October 2003 | ISSN: 0032-0781
Published online October 2003 | e-ISSN: 1471-9053 | DOI:
Functional Analysis of Isoforms of NADPH:Protochlorophyllide Oxidoreductase (POR), PORB and PORC, in Arabidopsis thaliana

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry


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NADPH:protochlorophyllide oxidoreductase (POR) catalyzes the light-dependent reduction of protochlorophyllide. To elucidate the physiological function of three differentially regulated POR isoforms (PORA, PORB and PORC) in Arabidopsis thaliana, we isolated T-DNA tagged null mutants of porB and porC. The mature seedlings of the mutants had normal photosynthetic competencies, showing that PORB and PORC are interchangeable and functionally redundant in developed plants. In etiolated seedlings, only porB showed a reduction in the photoactive protochlorophyllide and the size of prolamellar bodies (PLBs), indicating that PORB, as well as PORA, functioned in PLB assembly and photoactive protochlorophyllide formation in etiolated seedlings. When illuminated, the etiolated porB seedling was able to green to a similar extent as the wild type, whereas the greening was significantly reduced under low light conditions. During greening, high light irradiation increased the level of PORC protein, and the greening of porC was repressed under high light conditions. The porB, but not porC, etiolated seedling was more sensitive to the far-red block of greening than the wild type, which is caused by depletion of endogenous POR proteins resulting in photo-oxidative damage. These results suggest that, at the onset of greening, PLBs are important for efficient capture of light energy for photoconversion under various light conditions, and PORC, which is induced by high light irradiation, contributes to photoprotection during greening of the etiolated seedlings.

Keywords: Keywords: Arabidopsis thaliana — NADPH:protochlorophyllide oxidoreductase — Prolamellar bodies — Protochlorophyllide — Plastid differentiation.; Abbreviations: Chl, chlorophyll; Col, Columbia; FR, far-red; HL, high light; LHPP, light-harvesting POR Pchlide complex; LL, low light; ML, medium light; PAM, pulse-amplitude-modulation; Pchlide, protochlorophyllide; PLBs, prolamellar bodies; POR, NADPH:protochlorophyllide oxidoreductase; UBQ gene, ubiquitin gene; Ws, Wassilewskija.

Journal Article.  9062 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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