How do plants tell time?
The circadian system is a biological time-keeper comprised of inputs (light, temperature, stress), an oscillator (a gene regulatory network) and outputs (physiology, metabolism, development). It influences almost all aspects of the plant and allows them to anticipate daily changes in the environment and adapt to seasonal conditions (Haydon et al., 2019). The circadian clock is a core focus of research in the lab. Our main interest is to define the roles of metabolism and nutrition within the plant circadian system. Most of our activity uses the model plant Arabidopsis thaliana, but we also incorporate work on crops and weeds. We consider mechanisms of gene transcription, translation and post-translational control that influence circadian rhythms. Our research aims to make advances to understand fundamental aspects of plant cell biology, but also generate opportunities to develop crops or agricultural practices that match specific growth environments.
Metabolic signals in the circadian system
We have previously shown that sugars, which are the major product of photosynthesis, affect circadian rhythms in numerous ways. There is transcriptional control of circadian period by sugars which requires the energy sensor SnRK1(Haydon et al., 2013; Frank et al. 2018). Sugars also affect amplitude of rhythms by post-transcriptional control of GIGANTEA (Haydon et al. 2017). More recently we continue to use the regulation of the circadian system by sugars to identify additional mechanisms of dynamic metabolic signalling in plant cells. Our approach has combined the power of transcriptomics and chemical biology to reveal a new role for superoxide, a reactive oxygen species (ROS), which influences transcriptional responses to sugars and growth. Current projects in the lab aim to define how sugars generate this metabolic signal and how it controls gene expression. The chemical biology approach allows us to investigate conservation of the signalling pathway in crops and weed species.
The time is ripe: ethylene and the clock
Ethylene is a plant hormone that controls plant development and promotes ripening. Ethylene can act as a signal to adjust circadian rhythms in plants. The effect is influenced by sugars and requires GIGANTEA (Haydon et al. 2017). We are investigating the mechanism by which ethylene affects circadian rhythms and the impact of ethylene signalling on circadian-regulated processes in Arabidopsis and wheat.
Research in the lab has been funded by the BBSRC and The Royal Society with additional support from the University of York and The University of Melbourne.