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Keeping in time with the heat: how oscillating temperatures set the plant circadian clock

Periodic Reporting for period 1 - KeepTimeWithTheHeat (Keeping in time with the heat: how oscillating temperatures set the plant circadian clock)

Reporting period: 2018-06-01 to 2020-05-31

Almost all processes in plants are in some way governed by their internal clock. Daily cycles of growth, photosynthesis, scent production and pathogen defense are crucial for plant fitness. Every morning, light re-sets the phase of the internal biological clock to ensure that it keeps cycling with a 24 hour period. In recent years, much progress has been made in understanding the mechanisms by which light re-sets the clock. Temperature oscillations also play a role in re-setting the clock. The mechanism by which temperature re-sets the clock is however poorly understood. This project aimed to discover the mechanism by which temperature cycles entrain the clock.

Global warming is expected to disproportionally affect night time temperatures. If night time temperatures are increased, it is likely that plants will have less exposure to temperature oscillations. I hypothesised that this may have implications for plant fitness, particularly in situations where light is limited. My preliminary results showed that temperature oscillations could influence how well a plant survives on first exposure to light. I proposed that when a seedling germinates under the ground, temperature oscillations entrain the biological clock and enable the seedling to prepare for potentially damaging daylight, before such light is reached.

This project had two objectives; to further define how temperature oscillations affect seedling survival on first exposure to light, and to investigate the mechanism underlying this trait.
The initial work in the lab was promising and consistent with the preliminary results and underlying hypothesis. At a certain point however, it was necessary to move the experimental set up to another growth facility. Work in the new facility made it clear that the position of the experimental set-up had a great influence on the measured output. It was decided that the large variation in seedling survival made it too difficult to draw any solid conclusions from this assay.

We therefore switched to a much slower method, making crosses between clock reporter lines and mutants of known components in temperature signalling networks. Unfortunately, we were unable to find a mutant that was completely lacking thermal entrainment of the clock. During the course of the project, we became aware of work from another lab that suggests that one of the clock components may itself be a novel temperature sensor. If this is true, it may explain why we were unable to identify external components that are required for thermal entrainment of the clock.

Despite the set-backs in this project, several new tools were generated that are likely to be useful for future research. Information gained from these tools will be disseminated widely in order to maximise their exploitation.
Due to the set-backs listed above, it was not possible to realise all of the goals of this proposal. As with all cutting-edge research, there is no guarantee that nature will behave as expected. That said, many biological tools were generated during the course of this work which will likely find use in other projects. I was able to learn a great deal of molecular biology techniques that will definitely assist in my future work. Ideas that were sparked from this project have already resulted in a successful funding application and so will lead to more advances along the road. There has been a great deal of knowledge transfer between myself and the group. The professional contacts that have been made will almost certainly lead to more international collaborations within Europe. The continued strengthening of the European plant science network will be instrumental in maintaining food security in the years to come.