Determining the Contribution of Tomato Fruit Photosynthesis to Fruit Development and Quality

Plant photosynthesis supports life on earth and our entire food chain. It is normally thought of as occurring in leaves but we are beginning to understand that significant productivity depends on photosynthesis in diverse plant organs where a new understanding is needed. A recent review has indicated that non-foliar photosynthesis can provide an important source of carbon for growth and development [1]. Fruit photosynthesis is particularly interesting, as many species (including tomato) undergo a shift from green photosynthetic (or partial photosynthetic) metabolism to fully heterotrophic metabolism on ripening. Photosynthesis in tomato fruit is fully functional, contributes between 10% and 20% of the total fixed carbon of the fruit and makes an important contribution to early fruit development [1].
This timely and exciting project will take this further to explore the hypothesis that engineering the Calvin cycle within fruit chloroplasts can drastically enhance yield, fruit size and nutritional quality. It brings together 3 groups with complementary expertise in photosynthesis and molecular physiology at NIAB EMR, Nottingham and Essex, giving an opportunity to gain experience in molecular and whole plant physiology. Transgenic plants produced with Fruit specific over-expression and down-regulation of genes of the Calvin-Benson cycle, SBPase and FBPaldolase, will be used to dissect the involvement of fruit photosynthesis in fruit development. Quantification of the rates of fruit photosynthesis and the impact on fruit developmental processes will take place using chlorophyll fluorescence imaging in whole fruit chambers and infra-red gas exchange analysis [2] in green and ripening fruits relative to leaves. The effect of short term and long-term environmental factors that regulates photosynthesis rate of fruit during growth will be assessed. Exploratory structural analysis of tissue will take place using cutting edge microscopy and tomography. Metabolites, micronutrients, fruit quality and pigment composition will be measured. The successful candidate will work in a friendly atmosphere within the science teams with a spirit of helping colleagues. You will join a cohort of 38 PhD students on a site with 202 ha in the heart of Kent.