Poster (Scientific congresses and symposiums)
Isolation and characterization of mutants deficient in four steps of the phylloquinone biosynthesis pathway in Chlamydomonas reinhardtii.
Emonds-Alt, Barbara; Remacle, Claire; Cardol, Pierre
2016European Networks Conference on Algal and Plant Photosynthesis - 2016
 

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Keywords :
Chlamydomonas; Phylloquinone; Photosynthesis
Abstract :
[en] In photosystem I (PSI), phylloquinone participates to electron transfer as secondary electron acceptor (A1). The phylloquinone biosynthesis pathway, previously characterized by reverse genetic in Synechocystis sp. PCC 6803, involves 8 enzymatic steps from chorismate [1]. In the green alga Chlamydomonas reinhardtii, characterization of phylloquinone biosynthesis was still partial and only one mutant deficient for MEND was characterized [2]. In the present work, we found MENA-H homologs in C. reinhardtii genomic database. In particular, MENF, MEND, MENC, and MENH catalytic domains are present in a single ORF (named PHYLLO by similarity to gene organisation in Arabidopsis). We then took advantage of the fact that a double reduction of plastoquinone (PQ) in PQH2 occurs in anoxia into the A1 site in the mend mutant, interrupting photosynthetic electron transfer [3], to isolate new phylloquinone-deficient strains. UPLC-MS analysis confirmed the absence of phylloquinone in four news mutants impaired in MENA, MENB, MENC (PHYLLO) and MENE. Despite this loss, men mutants are still able to grow in low light but are high light-sensitive. In low light, the level of active PSII in men mutants is identical to that of the wild-type, but the level of active PSI is reduced by 30-40% as assayed by spectroscopic measurements. This decrease is more pronounced when cells are exposed to high light intensities during 4 hours. The level of active PSI is ~ 10% of wild-type cells and the electron photosynthetic transfer is reduced accordingly. Reorganization of the photosynthetic apparatus following lack of phylloquinone in men mutants is discussed.
Disciplines :
Biochemistry, biophysics & molecular biology
Author, co-author :
Emonds-Alt, Barbara ;  Université de Liège > Département des sciences de la vie > Génétique et physiologie des microalgues
Remacle, Claire  ;  Université de Liège > Département des sciences de la vie > Génétique et physiologie des microalgues
Cardol, Pierre  ;  Université de Liège > Département des sciences de la vie > Génétique et physiologie des microalgues
Language :
English
Title :
Isolation and characterization of mutants deficient in four steps of the phylloquinone biosynthesis pathway in Chlamydomonas reinhardtii.
Publication date :
26 April 2016
Number of pages :
A0
Event name :
European Networks Conference on Algal and Plant Photosynthesis - 2016
Event place :
Qawra, Malta
Event date :
du 26 avril 2016 au 29 avril 2016
Audience :
International
Funders :
FRIA - Fonds pour la Formation à la Recherche dans l'Industrie et dans l'Agriculture [BE]
Available on ORBi :
since 25 May 2016

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