Epicycle

To function coherently, the pathways that control development in any multicellular organism must be initiated at the appropriate stage of the life cycle, but very little is known about how these two processes - life cycle progression and multicellular development - are integrated and coordinated. Epigenetic regulatory mechanisms are expected to play an important part in this process, providing a means to ensure that only the relevant genetic components are expressed at each stage of the life cycle.

Genetic analysis of mutants of the brown alga Ectocarpus identified a major life cycle transition regulator, encoded by the OUROBOROS (ORO) and SAMSARA (SAM) genes, that links life cycle progression to multicellular development. Both ORO and SAM are predicted to encode TALE-class homeodomain transcription factors (TALE HD TFs). Interestingly, TALE HD TFs have also been implicated in life cycle regulation in mosses, indicating that an extremely ancient life cycle regulatory system has been convergently recruited to control sporophyte development in the land plant and brown algal lineages.

The objective of this project was to elucidate the genetic and epigenetic processes associated with life cycle progression and the deployment of the sporophyte developmental program in the brown alga Ectocarpus. The project combined approaches designed to specifically dissect the regulatory pathway that includes the ORO and SAM proteins with approaches aimed at monitoring genome-wide epigenetic modifications (histone post-translational modifications) during life cycle progression.