Circadian rhythm of photosynthesis and concurrent oscillations of transcript abundance of photosynthetic genes in the marine red algaGrateloupia turuturu

Abstract

Many biological processes are under the control of an endogenous circadian clock, a prominent example within the plant kingdom being photosynthesis. Here we report a robust circadian rhythm of photosynthetic oxygen evolution in the marine red macroalga Grateloupia turuturu. The rhythm was obvious in continuous white light at irradiances ranging from 50 to 500 mmol photons m 72 s 71 . To assess whether this physiological rhythm was correlated with changes at the level of gene transcription in G. turuturu, abundance of the transcripts encoding the phycoerythrin a and b subunits and the ribulose 1,5 bisphosphate carboxylase/oxygenase (Rubisco) subunits was analysed under light-dark cycles (LD) and continuous illumination (LL). Abundance of both transcripts exhibited diurnal and circadian changes in G. turuturu. In LD conditions, abundance of the phycoerythrin transcript peaked between midday and late afternoon. This pattern was maintained under constant conditions (LL) for up to three cycles. For the Rubisco transcript, mRNA abundance started to increase in the morning and peaked around midday in LD cycles. In LL, Rubisco transcript abundance continued to oscillate, but the increase of mRNA started earlier, already during subjective night. Our results suggest control of both transcripts by the circadian clock in G. turuturu.

Depth-specific fluctuations of gene expression and protein abundance modulate the photophysiology in the seagrass Posidonia oceanica

“…This points towards the important role of PsbS in activating NPQ mechanisms in seagrasses, as described for terrestrial plants 34 35 36 37 . Photosynthesis is one of the most fundamental processes regulated by circadian clocks at both the metabolic and gene-expression levels 38 39 40 . Accordingly, mRNAs of most photosynthesis-related components, including cab genes encoding chlorophyll a/b binding proteins, and subunits of photosystems I and II, followed the daily pattern of photophysiological parameters and exhibited a clear diurnal rhythmicity in plants from both depths, with increasing levels slightly before or after sunrise, peak abundance around noon, and decreasing expression at dusk and night.…”

Distinct patterns of nitrate reductase activity in brown algae: light and ammonium sensitivity in Laminaria digitata is absent in Fucus species1

“…NR activity is influenced by circadian rhythms in plants (Pilgrim et al. 1993), but although circadian rhythms influence growth in Laminaria (Lüning 1994) and photosynthesis in some red macroalgae (Goulard et al. 2004), it is still largely unknown if NR activity in algae is also influenced by circadian rhythms (but see Ramalho et al.…”

“…NR synthesis and maintenance of NR activity requires recent exposure to nitrate and is inhibited by ammonium, a more reduced form of inorganic N (Vergara et al 1998). NR activity is influenced by circadian rhythms in plants (Pilgrim et al 1993), but although circadian rhythms influence growth in Laminaria (Lü ning 1994) and photosynthesis in some red macroalgae (Goulard et al 2004), it is still largely unknown if NR activity in algae is also influenced by circadian rhythms (but see Ramalho et al 1995).…”

Rhythm of The Night (and Day): Predictive metabolic modeling of circadian growth in Chlamydomonas

“…A more sustainable approach is the use of photosynthetic organisms that can grow on CO2; however, the development of photosynthetically derived fuels and chemicals has fallen far short of the touted potential because the unique demands of photosynthetic organisms have not been considered in the strain development process. For example, algae and cyanobacteria have extremely strong circadian rhythms (11)(12)(13) which control the expression of cellular transcripts, proteins, and metabolic fluxes (1, 12,14). Additionally, they are strongly entrained -cells that are removed from light/dark cycles will continue to display circadian behaviors for days afterward (15).…”