Aureochrome 1a Is Involved in the Photoacclimation of the Diatom Phaeodactylum tricornutum

Abstract

Aureochromes constitute a family of blue light (BL) receptors which are found exclusively in heterokont algae such as diatoms (Bacillariophyceae) and yellow-green algae (Xanthophyceae). Previous studies on the diatom Phaeodactylum tricornutum indicate that the formation of a high light acclimated phenotype is mediated by the absorption of BL and that aureochromes might play an important role in this process. P. tricornutum possesses four genes encoding aureochromes. In this study we confirm the nuclear localisation of the PtAUREO1a, 1b and 2 proteins. Furthermore we studied the physiology of light quality acclimation in genetically transformed P. tricornutum cell lines with reduced expression of the aureochrome 1a gene. The results demonstrate that the AUREO1a protein has a distinct function in light acclimation. However, rather unexpectedly AUREO1a seems to repress high light acclimation which resulted in a state of ‘hyper’ high light acclimation in aureo1a silenced strains. This was indicated by characteristic changes of several photosynthetic parameters, including increased maximum photosynthesis rates, decreased chlorophyll a contents per cell and increased values of non-photochemical quenching in AUREO1a silenced strains compared to wild type cultures. Strikingly, AUREO1a silenced strains exhibited phenotypic differences compared to wild type cells during cultivation under BL as well as under red light (RL) conditions. Therefore, AUREO1a might influence the RL signalling process, suggesting an interaction of AUREO1a with RL perception pathways.

Photoprotective and antioxidant responses to light spectrum and intensity variations in the coastal diatom Skeletonema marinoi

“…While blue is the wavelength with the highest level of energy and red with a lowest, both are harvested by pigments fuelling the photosynthetic machinery and are sensed by photoreceptors (Depauw et al ., ) inducing downstream cascades of metabolic and physiological reactions (Depauw et al ., ; Schellenberger Costa et al ., ; Brunet et al ., ).…”

Blue Light-induced Dimerization of Monomeric Aureochrome-1 Enhances Its Affinity for the Target Sequence

“…Schellenberger Costa et al (35) suggested that aureochrome 1a is involved in photoacclimination. Furthermore, Huysman et al (36) reported that it mediates induction of diatom-specific cyclin dsCYC2 and controls the onset of cell division, and suggested that it functions synergistically with the bZIP transcription factor bZIP10 to induce dsCYC2 transcription.…”

Transcript level coordination of carbon pathways during silicon starvation‐induced lipid accumulation in the diatom Thalassiosira pseudonana

“…For example, the expression of silicon transporters is up‐regulated during silicon starvation in diatoms (Hildebrand et al ., 1998), and genes in the photorespiratory pathway are up‐regulated during increased glycolate production (Parker et al ., 2004). Genes such as LHCX1 and AUREOCHROME 1‐a in Phaeodactylum tricornutum are known to be light‐responsive (Bailleul et al ., 2010; Costa et al ., 2013). In the case of AUREOCHROME 1‐a, the specific mechanism by which light regulates cell division through the activity of dsCYC2 (a diatom‐specific cyclin) has been elucidated (Huysman et al ., 2013).…”