14 ERA-CAPS PHYTOCAL: Phytochrome Control of Resource Allocation and Growth in Arabidopsis and in Brassicaceae crops

For plants, light is a signal that carries information about the environment, and a source of energy for photosynthesis. PHYTOCAL focuses on the interaction between phytochrome signalling and photosynthesis, and seeks to understand fundamental processes that make carbon (C) and nitrogen (N) resources available for plant growth. These unexplored connections underlie plasticity, which contributes significantly to yield variability in the field. Phytochrome photochemistry is exquisitely tuned to detect spectral changes indicative of nearby vegetation. This light-activated surveillance mechanism initiates changes in plant architecture, biomass formation and the timing of reproduction: traits that are strongly linked to crop yield. These changes in growth strategy require corresponding adjustments in resource deployment, yet we have no understanding of how this is accomplished.
PHYTOCAL builds on new research from the partner labs showing that cross talk between phytochrome and carbon signalling is central to C resource use efficiency and resource conservation. A principal aim will be to determine the role of phytochrome in C resource management. PHYTOCAL will also delineate the genetic basis and impact of shading-induced N re-allocation in canopies. This trait strongly impacts on N use efficiency and stand photosynthesis, and in many crops is closely linked to yield.
PHYTOCAL will conduct a systematic study across scales, delivering mechanistic information about signal integration, time-resolved transcriptome and metabolite profiles, and quantitative information about biomass accumulation, defined as the flux of carbon to protein and cell wall components, and growth dynamics. The experimental findings will be integrated into models to test hypotheses and to gain understanding at a system level. An aim will be to build models that predict the dual action of phytochrome and photosynthesis on resource management and biomass production. PHYTOCAL will run parallel work programmes in the reference species, Arabidopsis and the closely related crop Brassica rapa. The rapid life cycle and larger resource pool of the reference species will enable us to accelerate knowledge acquisition. B. rapa brings the advantage of larger size, and allows new insights to be directly applied to a food crop.

PHYTOCAL builds on new research from the partner labs showing that cross talk between phytochrome and carbon signalling is central to C resource use efficiency and resource conservation. It will test the following hypotheses: (i) phytochrome plays an influential role in coupling C resources to growth; (ii) phytochrome and photosynthesis signals cooperate to conserve night time C reserves, preventing starvation and growth arrest; and (iii) phytochrome and photosynthesis interact at dawn to delay the activation of energy costly processes until the light intensity is high enough to drive photosynthesis. PHYTOCAL will also delineate the impact and genetic basis of shading-induced N re-allocation in canopies. This trait strongly impacts on N use efficiency, and yield in many crops.
PHYTOCAL will conduct a systematic study across scales, delivering mechanistic information about signal integration, time-resolved transcriptome and metabolite profiles, and quantitative information about biomass accumulation, defined as the flux of carbon to protein and cell wall components, and growth dynamics. The experimental findings will be integrated into models to test hypotheses and to gain understanding at a system level. PHYTOCAL benefits from prior investment in modelling from partner labs: (i) a Phytochrome Signalling Model that regulates growth; and (ii) a modular Framework Model where environmental inputs (incl. light) control resource production and allocation to leaves and growth. These models will be amalgamated to produce models that predict the dual action of phytochrome and photosynthesis on resource management and biomass production.
PHYTOCAL will work in the reference species, Arabidopsis and the closely related crop Brassica rapa. The rapid life cycle and larger resource pool of the reference species will to enable us to accelerate knowledge acquisition. B. rapa brings the advantage of larger size, and allows new insights to be directly applied to a food crop.

Confronted by the competing pressures of a rapidly-increasing human population, decreasing available arable land, and a climate in flux, there has perhaps never been a time where increasing crop yields has been more urgent for the global economy and the environment. This project is squarely focused on the connection between C metabolism and allocation and growth, a link that has been largely overlooked in previous efforts for yield improvement. Moreover, global increases in CO2 levels will have highly variable impacts on plants, depending on their genetics and their environment, and FACE experiments point to the allocation of C for growth and N use efficiency as a feature that will limit plant productivity in these future conditions. The data and models proposed as major milestones for this project may aid in planning for plants in both agricultural and natural settings. Seen in terms of the main focus areas of ERA-CAPS 2014, thus PHYTOCAL will provide basic insights into adaptation to a changing climate and plant responses to biotic/abiotic stress, and will establish a pipeline to accelerate the transfer of findings from a model system to a crop plant grown in the countries of all three partners, thus contributing to food security. Existing connections to biotechnology companies by the partners will be leveraged to facilitate technology transfer and new product development.