Understanding the cellular role of aureochromes, a new type of blue light photoreceptors, in diatoms
Final Report Abstract
Diatoms play a key role in the marine primary production being a climate regulating CO2 sink factor. In recent studies it has been shown that photoreceptors fulfil a central function in light acclimation and physiological fitness in the natural environment. It is now well known that Aureochromes (AUREOs) are blue light receptors using a basic leucine zipper domain for DNA binding to act as a light regulated transcription factor. The genome of the diatom Phaeodactylum tricornutum contains genes encoding four Aureochrome paralogs (PtAUREO1a, 1b, 1c, and 2). Comparative transcriptome analysis of wildtype and PtAUREO1a deficient mutants have revealed that this gene can operate as a central switch to control the metabolic remodeling of the cell during light acclimation. However, so fa, the function of the other AUREOs was unknown. In this cooperative project with Prof. Dr. Kroth in Konstanz, who studied the mechanisms of gene regulation and interaction on the molecular level (see the respective report), we analyzed the physiological function of PtAUREO 1c comparing a TALEN based PtAUREO 1c KO mutant with wildtype cells in light shift experiments. We show that both cell types have an identical physiological performance (growth, photosynthetic activity) and biochemical cell composition under red light (RL), but upon a shift to blue light (BL) growth is strongly inhibited in wildtype cells, whereas in the PtAUREO1c KO mutant this inhibition is less severe. Obviously, cells grown in RL become sensitive to BL. This sensitivity is strongly controlled by PtAUREO1a and less strongly by PtAUREO1c. Cells cultivated in white light with significant contribution of BL acclimate to different light intensities without any difference between wildtype and PtAUREO1a deficient mutant. Transcriptome analysis of WT and PtAUREO1c mutant during the light shift from RL to BL support the hypothesis that Aureochromes are involved in a direct control of cell growth controlling pathways, especially on ribosomal biosynthesis. The major result of this project is the identification of the protein biosynthesis pathways as direct target of Aureochrome mediated gene control, which, in essence, controls cell division.
Publications
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Sensing and Signalling in Diatom Responses to Abiotic Cues. The Molecular Life of Diatoms, 607-639. Springer International Publishing.
Jaubert, Marianne; Duchêne, Carole; Kroth, Peter G.; Rogato, Alessandra; Bouly, Jean-Pierre & Falciatore, Angela
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Identification of promoter targets by Aureochrome 1a in the diatom Phaeodactylum tricornutum. Journal of Experimental Botany, 75(7), 1834-1851.
Im, Soo Hyun; Lepetit, Bernard; Mosesso, Niccolò; Shrestha, Sandeep; Weiss, Laura; Nymark, Marianne; Roellig, Robert; Wilhelm, Christian; Isono, Erika & Kroth, Peter G.
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Functional demonstration of Aureochrome 1a proteasomal degradation after blue light incubation in the diatom Phaeodactylum tricornutum. Journal of Plant Physiology, 292, 154148.
Im, Soo Hyun; Madhuri, Shvaita; Lepetit, Bernard & Kroth, Peter G.
