The Oscillation of Photosynthetic Capacity in <i>Lingulodinium polyedrum</i> is not related to differences in RuBisCo, Peridinin or Chlorophyll <i>a</i> Amounts

Abstract

Abstract We examined the rhythm of photosynthesis in the dinoflagellate Lingulodinium polyedrum to determine if the rhythms were due to changes in pigments levels or RuBisCo (ribulose 1,5-biphosphate carboxylase-oxygenase) in cells exposed to either light : dark (12 :12 h) or constant dim light conditions. HPLC analyses detected no significant changes in peridinin nor chlorophyll a amounts. Although β-carotene showed a similar oscillation to photosynthetic capacity, this pigment comprises as low as 4% of the total carotenoids and therefore could not be responsible for this rhythm. Northern and Western blot analyses showed that RuBisCo transcripts and protein levels remain constant over the day. The results support the hypothesis that circadian changes in RuBisCo distribution inside individual chloroplasts accounts for the rhythm of carbon fixation in dinoflagellates.