Evolution, development, and mechanisms of floral organ photosynthesis.

Food security and climate change are two of the most important challenges facing modern society. Increased crop productivity is required to provide enough food for an ever-growing population, however, this should not come at a cost of increased carbon emissions. Novel plants variants that can use less land, capture more carbon, and produce higher yields are needed.
Many research groups around the globe are working on improving photosynthesis to meet these challenges, which includes modifying enzymes and changing the anatomy of the leaf to capture more carbon. However, relatively few groups have focused on improving photosynthesis that occurs outside of the leaf, in stems, flowers and fruits. Many species heavily rely on non-leaf photosynthesis, however, there are many aspects of this process that we do not understand.
This project aims to understand more about non-leaf photosynthesis: How has nature used it to improve plant health? How is it programmed on a genetic level? How can we manipulate it to benefit nature and society? We will focus our efforts initially on the mustard plant family because they contain 'model' plants as well as important crops, such as oilseed rape. Model plants are plants that are well-characterized (e.g. have a sequenced genome) and whose genome we can modify with ease. This is important because understanding how a complex process such as non-leaf photosynthesis functions requires the availability of tractable systems to test specific hypotheses. This power of this approach has been demonstrated recently with the development of plants with shatter-resistant fruits in oilseed rape, which reduces harvesting losses significantly. These plants were generated by directly using knowledge acquired from model plants.
Here, we will employ a similar strategy. First, we will develop our understanding of non-leaf photosynthesis on genetic and physiological levels. Next, we will use this knowledge to make specific hypotheses on how to modify non-leaf photosynthesis to improve agriculturally important traits. We will test these hypotheses in both model and crop plants and develop improved varieties in a step-wise manner.
Although we will initially investigate species in the mustard plant family, this work will also be relevant to species in other plant families including wheat, barley, and tomato, whose flowers and fruits also perform photosynthesis. Therefore, this project marks the beginning of a long-term goal to understand the evolution of non-leaf photosynthesis and to develop strategies to modify it in important crop plants.

A large number of domestication genes encode transcription factors (TFs), with MADS-domain TFs being highly represented. Preliminary data supports the role of the MADS-TF AGAMOUS (AG) as a regulator of floral organ photosynthesis (FOP), which makes an important contribution to fruit quality, seed viability and/or abiotic resistance in a variety of species. Our lack of understanding of the phenotypic and genetic variation underlying FOP is impeding our ability to exploit it to improve crop performance. This proposal aims to rectify these issues with a series of targeted objectives.
We will use a combination of single cell transcriptomics, comparative transcriptomics, comparative protein localization experiments and comparative development/physiology to characterize the genotypic and phenotypic space of FOP in the fruits of the Brassicaceae. These systematic descriptions will provide an understanding of the variation that exists during the establishment of FOP and its activity. With this knowledge in hand, strategies to modify FOP will be developed and explored during this proposal and in the future. This work can be translated to understand FOP in other species, such as tomato and wheat, in which FOP is known to play an important role.
Additional benefits from this work includes an improved understanding of TF activity in plants. In particular, the evolution of gene regulatory networks will be explored through comparative protein localization experiments, of which there are few examples in plants. We will further explore the differentiation of floral organs and the establishment of cellular identity using state-of-the-art techniques, which will also help to further reveal how MADS-TFs modulate leaf identity to produce floral organs.
In sum, this proposal will provide specific strategies to modify FOP to improve crop performance, and provide detailed insights into the evolution of the mechanisms underlying FOP, floral organ development and gene regulatory networks.

(1) Crop scientists. In principle, modifying floral organ photosynthesis can improve seed quality and/or improve water usage efficiency. Although there may be limited scope to realize these potentials during the project, by giving public talks, connecting on social media, and contributing to the Oilseed Genetic Improvement Network (OREGIN), communication of this work can promote the potential to use floral organ photosynthesis to improve crop performance.
(2) Agribusiness. The potential to increase seed oil content through floral organ photosynthesis will be thoroughly explored, and closer connections with seed oil companies will be made by proposing collaborative efforts. The broader potential to increase grain yield in wheat and barley will also be proposed to companies that have elite cultivars, in order to explore floral organ photosynthesis (e.g. in awns). To this end, I have made contact with the seed company KWS to explore the potential of this research to be applied to agribusiness.
(3) Policy makers. The increasing pressure to increase crop yields while reducing environmental impact is likely to lead to a drastic overhaul of agricultural practices. Policy makers are sure to explore every option to harmonize these goals. The potential of floral organ photosynthesis to contribute to solutions for these challenges will be highlighted through social media, and other press releases following paper publications.
(4) UK Science base. The technician and PDRA associated with the programme, and myself, will benefit through being trained in state-of-the-art genomic and transcriptomic techniques (FACS and single-cell sequencing), and techniques to measure photosynthetic activity. The technician will be provided with further training in standard molecular techniques (DNA extraction, PCR assays, cloning, plant transformation), as well as the essentials for cultivating Brassica plants. Furthermore, the technician will be provided with training at the University of Essex for measurements of photosynthetic activity in collaboration with Prof. Tracy Lawson. The PDRA will be trained in chromatin immunoprecipitation, gene expression analysis and genome-editing. Additional skills, applicable to alternative employment sectors, include independent management of small individual projects (e.g. management of plant growth for the technician, or a full experiment for the PDRA); the ability to formulate solutions for problems and effectively communicate them; and, developing the confidence to make decisions based on critical evaluation of given information. I will further benefit from an increased focus on floral organ photosynthesis and comparative approaches to develop my research profile. Moreover, all these techniques can be transferred into new collaboration projects widening the impact on the UK scientific community. These benefits will be realised during the timeframe of the project programme.