Diatoms are predominant unicellular organisms in marine and freshwater ecosystems that encounter intense variations in their environment. Thus, in order to survive, diatoms must be able to control their cell and life cycle rhythms to a variety of different conditions.
As a model system to connect cell division with environmental conditions, diatoms stand out, as their proliferation depends strongly on stimuli such as light and nutrients. Among microalgae, diatoms represent not only one of the most species-rich classes, they are as well solely responsible for about 40% of all oceanic carbon fixation. Diatoms possess a highly chimeric genome arisen through endosymbiotic and horizontal bacterial gene transfers, resulting into a unique melting pot of diverse metabolic and biochemical pathways, likely contribution to their ability to their evolutionary and ecological success. They thrive in well-mixed water columns of temperate and polar oceans and lakes, beneath sea ice and in the plankton or on sediments of coastal seas and estuaries. Previously we identified the diatom dsCYC2 gene as the final target of the signalling cascade linking light perception with cell cycle onset. Using this observation, we aim to unravel the physiological and molecular mechanisms that link light signaling to the cell cycle in diatoms in order to understand how diatoms can respond adequately to rapidly changing light conditions in the oceans. To this end we perform an in-depth characterization of dsCYC2/CDK complex activation by combining genomics with biochemical assays.
Phaedactylum tricornutum / Seminavis robusta
The defining feature of diatom biology and key to understanding their evolutionary success is their haplo-diploid life cycle, controlled by a unique, endogenous cell size reduction-restitution strategy that is used as a clocking mechanism to switch resources to cell differentiation and sexual reproduction. Yet, very little is known about the regulatory mechanisms and signaling pathways underlying diatom cell division, cell size control, and sexual reproduction. In collaboration with Prof. Wim Vyverman and Prof. Koen Sabbe (UGent), we aim to characterize mechanisms of diatom mating. As a first objective, we aim to unravel the mechanisms that determine the mating type of diatoms. Secondly, we aim to uncover the signaling cascades involved in the cell size-dependent sexual differentiation and maturation, and the sexual reproduction itself. Our results will be useful for the cultivation and breeding of microalgae, which are an enormous but largely untapped source of bio-active compounds for the pharmaceutical, food, and cosmetics industries, as well as metabolic pathways that may provision our future energy needs.
Huysman M.J.J., Tanaka A., Bowler C., Vyverman W., De Veylder L. (2015). Functional characterization of the diatom cyclin-dependent kinase A2 as a mitotic regulator reveals plant-like properties in a non-green lineage. BMC Plant Biol. 14, 15:86.
Huysman M.J.J., Vyverman W. and De Veylder L. (2014). Molecular regulation of the diatom cell cycle. J. Exp. Bot. 65, 2573-2584.
Huysman M.J.J., Martens C., Vyverman W. and De Veylder L. (2014). Protein degradation during the diatom cell cycle: annotation and transcriptional analysis of SCF and APC/C ubiquitin ligase genes in Phaeodactylum tricornutum. Mar. Genom. 14, 39-46.
Huysman M.J.J., Fortunato A.E., Matthijs M., Schellenberger Costa B., Vanderhaeghen R., Van den Daele H., Sachse M., Inzé D., Bowler C., Kroth P.G., Wilhelm C., Falciatore A., Vyverman W. and De Veylder L. (2013). AUREOCHROME1a-mediated induction of the diatom-specific cyclin dsCYC2 controls the onset of cell division in diatoms (Phaeodactylum tricornutum). Plant Cell 25, 215-228.
Huysman M.J.J., Martens C., Vandepoele K., Gillard J., Rayko E., Heijde M., Bowler C., Inzé D., Van de Peer Y., De Veylder L. and Vyverman W. (2010). Genome-wide analysis of the diatom cell cycle unveils a novel type of cyclins involved in environmental signalling. Genome Biol. 11, R17.