UV induced phycobilisome dismantling in the marine picocyanobacterium Synechococcus sp WH8102

Ludovic Joubin

Description

Niveau: Secondaire, Lycée, Terminale
REGULAR PAPER UV-induced phycobilisome dismantling in the marine picocyanobacterium Synechococcus sp. WH8102 Christophe Six Æ Ludovic Joubin Æ Frederic Partensky Æ Julia Holtzendorff Æ Laurence Garczarek Received: 13 October 2006 / Accepted: 7 April 2007 Springer Science+Business Media B.V. 2007 Abstract The marine picocyanobacterium Synechococ- cus sp. WH8102 was submitted to ultraviolet (UV-A and B) radiations and the effects of this stress on reaction center II and phycobilisome integrity were studied using a com- bination of biochemical, biophysical and molecular biology techniques. Under the UV conditions that were applied (4.3 W m–2 UV-A and 0.86 W m–2 UV-B), no significant cell mortality and little chlorophyll degradation occurred during the 5 h time course experiment. However, pulse amplitude modulated (PAM) fluorimetry analyses revealed a rapid photoinactivation of reaction centers II. Indeed, a dramatic decrease of the D1 protein amount was observed, despite a large and rapid increase in the expression level of the psbA gene pool. Our results suggest that D1 protein degradation was accompanied (or followed) by the dis- ruption of the N-terminal domain of the anchor linker polypeptide LCM, which in turn led to the disconnection of the phycobilisome complex from the thylakoid membrane. Furthermore, time course analyses of in vivo fluorescence emission spectra suggested a partial dismantling of phy- cobilisome rods.

• fluorescence emission


• pe always binds


• tca-induced precipitation


• rna pellets


• pcr-s11 medium


• quantitative pcr


• uv stress


• grown synechococcus sp


• synechococcus sp

Sujets

• Première
• Forward
• Louis Joubin
• Holtzendorff
• Real-time polymerase chain reaction

Informations

• Publié par: profil-zyan-2012
• Nombre de lectures: 19
• Langue: English

Extrait

Photosynth Res DOI 10.1007/s1112000791704

R E G U L A R P A P E R

UVinduced phycobilisome dismantling picocyanobacteriumSynechococcussp.

Christophe SixÆLudovic JoubinÆ Frédéric Partensky Æ Julia Holtzendorff ÆLaurence Garczarek

Received: 13 October 2006 / Accepted: 7 April 2007  Springer Science+Business Media B.V. 2007

AbstractThe marine picocyanobacteriumSynechococ cussp. WH8102 was submitted to ultraviolet (UVA and B) radiations and the effects of this stress on reaction center II and phycobilisome integrity were studied using a com bination of biochemical, biophysical and molecular biology techniques. Under the UV conditions that were applied –2 –2 (4.3 W m UVA and 0.86 W m UVB), no significant cell mortality and little chlorophyll degradation occurred during the 5 h time course experiment. However, pulse amplitude modulated (PAM) fluorimetry analyses revealed a rapid photoinactivation of reaction centers II. Indeed, a dramatic decrease of the D1 protein amount was observed, despite a large and rapid increase in the expression level of thepsbAgene pool. Our results suggest that D1 protein degradation was accompanied (or followed) by the dis ruption of the Nterminal domain of the anchor linker polypeptide L CM , which in turn led to the disconnection of the phycobilisome complex from the thylakoid membrane. Furthermore, time course analyses of in vivo fluorescence emission spectra suggested a partial dismantling of phy cobilisome rods. This was confirmed by characterization of isolated antenna complexes by SDSPAGE and immuno blotting analyses which allowed us to locate the disruption site of the rods near the phycoerythrin I—phycoerythrin II junction. In addition, genes encoding phycobilisome com ponents, includingasubunits of all phycobiliproteins and phycoerythrin linker polypeptides were all down regulated in response to UV stress. Phycobilisome alteration could be

C. SixL. JoubinF. PartenskyJ. Holtzendorff L. Garczarek (&) Station Biologique, UMR 7144 CNRS et Université Pierre et Marie Curie, B.P. 74, 29682 Roscoff cedex, France email: garczare@sbroscoff.fr

in the marine WH8102

the consequence of direct UVinduced photodamages and/ or the result of a proteasemediated process.

KeywordsPhotoinhibitionPhotosystem II PhycobilisomePhycoerythrinSynechococcus UV

Introduction

The impact of UV radiations on the physiology of photo synthetic cells, in particular cyanobacteria and algae, has been extensively studied (see, e.g., Holzinger and Lutz 2006al.; Sinha et 2001; Xue et al.2005). Damages to nucleic acids, proteins, and lipids may occur either by di rect photochemical reaction or by indirect oxidation, due to reactive oxygen species induced by UVB (He and Hader 2002a,b,c; He et al.2002). Although DNA damages are often considered as the main lethal cause of these radia tions, UV also strongly affect components of the photo synthetic apparatus, among which light harvesting complexes and reaction center II (RCII) constitute primary targets. In cyanobacteria, Lao and Glazer (1996) calculated that phycobilisome (PBS) components and chlorophyll binding proteins accounted for more than 99% of the UV absorption and they estimated that UVB damage to these lightharvesting complexes may significantly exceed that to DNA. The involvement of the RCII protein D1 (and to a least extent D2) in the response to UV stress has been clearly evidenced in higher plants (Barbato et al.2000; Strid et al.1994), algae (Xiong2001) and cyanobacteria (Campbell et al.1998al.; Sicora et 2006; Vass et al. 1999). In particular, cyanobacteria often possess multiple copies of thepsbAgene which encode either constitutive D1 protein or an inducible form of this protein thought to

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