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In vivo study of the Protochorophyllide Oxydoreductase A function in Arabidopsis thaliana

Abstract : Gymnosperms, mosses and green algae are able to turn green even in the dark. In contrast, chlorophyll biosynthesis is blocked in angiosperms at its penultimate step, the reduction of protochlrophyllide into chlorophyllide. This reaction is catalyzed by the NADPH: protochlorophyllide oxidoreductase (POR), whose function is entirely light-dependent. Three POR isoforms (PORA, PORB and PORC) have been identified in Arabidopsis thaliana and their expression have been mainly studied at the transcript level. We have therefore decided to analyze both POR transcript and protein accumulation during plant development. We have confirmed that POR gene expression is tightly regulated by light: much like their transcripts, the PORA and PORB proteins are mainly accumulated in the dark while PORB and PORC are mainly observed in the photosynthetic tissues. However, weak levels of both PORA transcript and protein were detected in the light, raising the intriguing question of the possible role of PORA beyond skotomorphogenesis.Up to now, the studies concerning the role of the PORA enzyme are indirect. We have therefore decided to investigate the function of the protein more in details using independent porA mutants. Among them a knock out porA line presents a complex phenotype, in which defects in the photosynthetic process have been identified. We have also obtained a double mutant that is KO for both the PORA and PORB alleles. The comparison of the porA porB double mutant with the porA mutant has show that the PORA and PORB isoforms are functionally redundant in the establishment of the prolamellar bodies in cotyledons of etiolated plants. Our results also suggest that PORA may act as photoprotector.
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https://tel.archives-ouvertes.fr/tel-00256027
Contributor : Laurence Bolling <>
Submitted on : Thursday, February 14, 2008 - 4:17:13 PM
Last modification on : Friday, November 6, 2020 - 4:12:27 AM
Long-term archiving on: : Thursday, May 20, 2010 - 6:55:25 PM

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  • HAL Id : tel-00256027, version 1

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Laurence Bolling. In vivo study of the Protochorophyllide Oxydoreductase A function in Arabidopsis thaliana. Biologie végétale. Université Joseph-Fourier - Grenoble I, 2007. Français. ⟨tel-00256027⟩

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