PhD Studentship: Green Perfect for Improved Agronomic Performance: Investigation of a Cellular Chloroplast Compartment’s Regulator Using Genetics and Advanced Imaging

The biology of chloroplasts underpins the biology of whole plants, and the two most-important impacts of plants for humanity: as food source and carbon sink. Yet a surprising number of aspects of chloroplast biology remain poorly understood. 

Chloroplast development is under the control of the plant cell’s nucleus. A fundamental question arises from the fact that all cells in a plant carry the same nuclear genetic information, yet different cell types in different organs carry vastly different chloroplast complements. How does this occur? How do cells turn chloroplast development on? When do they stop, at different points for different cell types? Why do mesophyll cells, those with the largest chloroplast complement, produce one layer, but no more, of chloroplasts sandwiched between the internal vacuole and the plasma membrane? Why do other “bundle sheath cells”, photosynthetic but different from mesophyll cells, associated to vascular bundles, and a key target of the International “C4 Rice Project, have a reduced chloroplast compartment, and can we increase the chloroplast content? 

Our laboratory at Royal Holloway devised two novel genetic screens which sought what have been postulated as “green switches” (Cackett et al. 2022) driving chloroplast development, or their negative regulators. The lab has previously successfully identified important genes for chloroplast developmental processes using genetics (mutant isolation, gene identification and analysis of gene function, see Loudya et al. 2022).  The genetic screen made use of previous knowledge  which confirmed the value but also revealed the limit of the function of a known family of transcription factors (Loudya et al. 2021). The laboratory identified one key mutant which exhibited significantly enhanced chloroplast content in both mesophyll and bundle sheath cells of the genetic model plant, Arabidopsis thaliana and, in preliminary experiments, improved growth. This mutant, and the gene identified as a result, reveal a potential avenue for translation towards crops with improved productivity. The mutant also causes delayed flowering, a trait which is or is not desirable in crops, depending on conditions.  In this project you would seek further mutations which retain the enhanced chloroplast compartment but remove the delayed flowering.  The screening will make use, among other techniques, of hyperspectral imaging.  Mutants obtained will have their underlying genes identified and their mode of action studied. The combined new and existing gene modifications will be the basis for future translation into crops by our commercial partner, Wild Bioscience. This company is a spin-off of Oxford University, focused on the enhancement of photosynthesis of improved crop performance and, while only a young start up, its work has already been the subject of significant media interest (see below). The  PhD will be jointly supervised by Royal Holloway and Wild Bioscience, and will involve a 3-month placement at the company facilities.

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