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Cellular social networks of organelles

Principal Supervisor: Dr Iain G. Johnston, School of Biosciences

Co-supervisor: Professor George Bassel, School of Biosciences

PhD project title: Cellular social networks of organelles

University of Registration: University of Birmingham

Project outline:

Plant bioenergetic organelles are pivotal players in feeding the world and powering complex life. Contrary to their rather boring, static textbook pictures, these organelles form fascinating and beautiful dynamic structures in cells, rapidly moving through the cell like cars in a city, and fusing and breaking apart under the microscope even as one watches (see data from the lab at http://www.youtube.com/watch?v=G3tuH4DOKzY ). The cell invests energy into powering and controlling these dynamics, which are vital for metabolic function and crop productivity. However, the cellular benefits of this rich behaviour remains mysterious. Understanding why the cell controls its organelles in this way will answer long-standing scientific questions and open new avenues to understanding and engineering plant metabolism for increased crop robustness and productivity.

Thanks to modern microscopy and fluorescently-labelled plant lines, the physical behaviour of plant organelles has been revealed in exquisite and rich detail. We can now characterise the “social networks” of organelles, tracking over time which mitochondria and chloroplasts meet and part ways. This affords the unprecedented opportunity to test different ideas about what the cell may be accomplishing through controlling its organelles. We also have access to a very recently constructed plant line where ATP concentration within cells can be measured with microscopy, allowing us to observe links between organelle behaviour and the cellular energetic budget, allowing us for the first time to build a complete picture of the dynamic “energy landscape” of the cell.

A particularly compelling example of the importance of organelle position can be found in C4 photosynthesis. C4 is a remarkable, complex union of evolutionary innovations that has emerged from convergent evolution over 60 times. C4 offers many advantages over “traditional” C3 photosynthesis, but several important crop plants including rice and barley have not evolved C4. There is therefore great agricultural and economic interest in understanding how C4 emerges. Our previous work has shown that one step that may “prime” plants to proceed down this pathway is the rearrangement of organelles in cells [2]: in many C4 species, mitochondria and chloroplasts take up specific positions in some photosynthesising cell types [3];

tightly packed at one side of the cell relative to the vasculature. What does this arrangement bring to the cell? Can we mimic it in other crops to increase efficiency? More generally, how does the rich and controlled physical behaviour of plant organelles influence metabolism, and can we use this knowledge to rationally design better crops?

This project will use fluorescence microscopy at the UoB’s excellent facilities and computational modelling approaches (full training will be provided in both sets of approaches) to explore the vital, but unknown, fundamental principles governing organelle motion and behaviour. The researcher will develop highly valuable and transferrable expertise in cutting-edge statistical and machine learning methods to link experiment with theory to make both “blue skies” and translatable scientific progress.

This project would suit students interested in exploring vital but understudied aspects of cell biology – physical motion, intracellular heterogeneity in metabolites, and physical relationships between organelles. Some mathematical or computational background, and some experience of microscopy would be valuable, and enthusiasm in developing these interests is essential.

References:

  • El Zawily et al., Plant Physiol 166 808 (2014)
  • Williams & Johnston et al., eLife 2 e00961 (2013)
  • Muhaidat et al., Plant Cell Environ 34 1723 (2011)

BBSRC Strategic Research Priority: Food Security

Techniques that will be undertaken during the project.:

  • Plant growth
  • Genetic transformation
  • Live-cell imaging
  • Fluorescence microscopy
  • Systems biology
  • Computer simulation
  • Machine learning

Contact:Dr Iain G. Johnston, School of Biosciences