A holistic approach to improve the photosynthetic perfromance and productivity of C3 crops under diverse environmental conditions

The PhotoBoost project addresses the widening gap between agricultural productivity and the global market demand for food/feed and bioenergy crops in an environmentally friendly manner by increasing the efficiency of photosynthetic CO2 fixation. This will be achieved by developing enhanced C3 crops that combine two or more of the following approaches: a) the optimisation of light reactions; b) the integration of an algal CCM; c) the introduction of an engineered photorespiratory bypass mechanism, improved by the knockout of the native plastid glycolate-glycerate transporter; and d) the optimisation of source-sink capacity, improved by the knockout of phloem-mobile tuberisation signal SP6A, thus enhancing the resilience of heat-sensitive cultivars to climate change. The consortium members have increased photosynthetic efficiency by up to 15% using individual approaches, but the stacking of multiple approaches in the same plant has never been attempted before. We will also explore e) the adaptation of stomatal conductance to improve the water-use efficiency, and f) the integration of an O2 scavenging mechanism as a novel strategy to boost photosynthesis. Experience from past and/or ongoing EU and B&MGF projects clearly indicates that although the individual approaches can be effective, they are insufficient to achieve the ambitious objectives of the current call. Therefore, the PhotoBoost project will generate optimised lines representing two major food crops (potato and rice) by simultaneously targeting multiple constraints limiting photosynthetic efficiency. We aim to increase photosynthetic efficiency under diverse environmental conditions by at least 20–25% in terms of photosynthesis rates and by at least 25–30% in terms of biomass yield. Our published results demonstrate that such approaches are viable and there is no a priori reason to doubt that combining multiple approaches in the same plant will achieve even higher levels of biomass yield and productivity.