A Structural and Molecular Atlas for Early Leaf Development in Rice (Oryza sativa)

Rice is one of the most important crops in the world, and several global projects are underway to improve its photosynthetic performance to secure yields. Such projects rely on fundamental alterations to leaf development to change its anatomy and biochemistry. To date, the majority of studies of rice leaf development have focussed on the spatial development of already maturing leaves, which may differ from temporal development as the leaf forms de novo. In this thesis, I focus on this temporal development, and report a morphological and metabolic characterisation of its early stages. In Chapter 2, I use scanning electron microscopy to document the temporal development of leaf primordia. I have produced a novel image dataset describing the epidermal differentiation pattern of early development. Use of this technique across two lines of domestic and two lines of wild rice has shown a conservation of epidermal patterning during development. Further, I have created a developmental index to allow for accurate developmental staging of leaf primordia too small to judge by eye. In Chapter 3, I have developed a protocol to examine the metabolite fingerprints of individually dissected leaf primordia using mass spectrometry. This technique can be used to distinguish between metabolic profiles over different stages of leaf development. This work has identified metabolites to act as potential developmental markers, and suggests that flux through the tricarboxylic acid (TCA) cycle is also indicative of developmental stage. Finally, in Chapter 4 I describe a set of experiments examining the relationship between leaf anatomy and photosynthetic performance in a genetically engineered rice population with variation in individual anatomical parameters. In this study, there is no correlation between photosynthetic performance and any individual structural trait. This highlights the need for careful consideration of genetic constructs, and a greater knowledge of the leaf developmental trajectory.