Dr Hannah Rees

I am interested in circadian rhythms in wild and crop plants; particularly how they vary in nature and how we can manipulate rhythms to improve agricultural potential. My background is in molecular biology (eg: RT-qPCR and RNA-sequencing) and imaging-based approaches (e.g: Delayed fluorescence imaging, fluorescent reporters, confocal microscopy) to study circadian traits. I have previously used a mixture of experimental biology and bioinformatics to study rhythms in Arabidopsis, Brassica, wheat and bryophytes. I completed my PhD with Professor Anthony Hall at Liverpool University and the Earlham Institute. My thesis was entitled “Time for crops : an exploration of circadian variation in model and crop plant species”. Projects during my PhD included using confocal microscopy in combination with fluorescent reporters to track circadian expression of core clock proteins at the single cell level, and adapting a delayed fluorescence (DF) imaging method to study differences in the clock between Brassicas and wheat. Later in my PhD, I became interested in quantifying naturally occurring variation in circadian rhythms. I used DF imaging to phenotype 191 accessions from Sweden which allowed me to conduct the first GWA analysis using circadian phenotypes as a trait. After my PhD, I stayed at Earlham to complete a Post-doc investigating the circadian transcriptome in hexaploid wheat.

I believe circadian research in plants is important for several reasons:

1. The circadian clock regulates agronomically relevant traits.

These include: water use efficiency, nitrogen utilisation, photosynthetic efficiency, starch utilisation, resilience to pathogens and pests, tolerance to cold, heat, photo damage and osmotic stress and flowering time (or heading dates) and seasonal accuracy. It has also been shown that plants with a circadian clock that is synchronised to the external environment have increased survival and higher yields. I am interested in finding ways to modify circadian rhythms to create varieties with improved agronomic traits and identifying existing cultivars with rhythms that might make them suited to growth in particular environments.

2. We still don’t fully understand how much variation in circadian phenotypes is present in crop cultivars.

Until we appreciate how circadian rhythms vary due to natural environmental pressures or human selection, we cannot identify the circadian traits which make a plant suitable to growth in particular environments.

 

3. The circadian clock regulates ecosystem interactions

The state of circadian rhythms influences the types of interactions a plant has with its environment and how successful it is as a result. Rhizospheres of plants with altered circadian rhythms are significantly different compared to wild-type plants and correct phasing of the clock is essential for targeted interaction with pollinators and defence from herbivores. I am interested in how existing variation in circadian traits might influence these factors in crop plants.

 

4. The circadian clock changes over the life of the plant

It has been shown that senescence and developmental timing is often altered in mutants for core clock components. Conversely, the period length (pace of the clock) changes in aging leaves and it has been hypothesised that both aging and the circadian clock are involved in regulating leaf senescence. I am interested in how an oscillator whose primary function is to track 24h day-night cycles can have a role in timing developmental processes over the life cycle of a plant. It is possible that lessons learned about the clock and aging in plants might be more widely applicable to other model systems and even humans.

• Crop Genomics