|Reference : Importance of the alternative pathway of respiration for avoidance of ROS production and...|
|Scientific congresses and symposiums : Unpublished conference|
|Life sciences : Biochemistry, biophysics & molecular biology|
|Importance of the alternative pathway of respiration for avoidance of ROS production and for optimisation of photosynthesis in Chlamydomonas|
|Franck, Fabrice [Université de Liège - ULg > > Biochimie végétale >]|
|Dinant, M. [ > > ]|
|Cardol, P. [ > > ]|
|Remacle, Claire [Université de Liège - ULg > Département des sciences de la vie > Génétique >]|
|Matagne, René-Fernand [Université de Liège - ULg > Services généraux (Faculté des sciences) > Relations académiques et scientifiques (Sciences) >]|
|13th International Chlamydomonas Conference|
|[en] alternative oxidase ; Chlamydomonas reinhardtii ; photosynthesis|
|[en] The physiological function of the alternative pathway of respiration has been investigated by analysing two RNAi C.reinhardtii lines deprived of alternative oxidase protein (AOX1). Compared to wild-type, AOX1- lines exhibited modified growth curves and reduced maximal cell density. These differences were more pronounced at high irradiance and in nitrate-containing medium (TAP NO3) rather than in ammonium-containing medium (TAP NH4). Although the alternative pathway was inactive, respiration was not significantly altered in transgenics. Light-saturation curves of O2-evolution were only slightly modified. However, non-photochemical quenching of fluorescence (NPQ) was strongly reduced. Further analysis showed that AOX1- transgenics present a reduced ability to promote the change in energy distribution between photosystems, known as state transition. This effect, which explains low NPQ in the light, was most pronounced in high-light cells cultivated in TAP NO3 medium. Moreover, AOX1- transgenics exhibited higher levels of intracellular peroxides, which suggests that inhibition of state transition might result from higher ROS production. In support of this hypothesis, addition of millimolar-range concentrations of H2O2 to wild-type inhibited the state transition promoted by the reduction of the plastoquinone pool in darkness.|
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