Within WP1, e-photosynthesis was combined with the Ball-Berry-Woodrow model to improve the representation of stomatal dynamics and optimise water-use efficiency. This enabled calculation of CO2 assimilation and stomatal conductance subject to environmental parameters specified for e-photosynthesis. In addition, crop-specific kinetic parameters and rate equations were introduced to improve the representation of the mechanisms underlying non-steady-state photosynthesis in the e-photosynthesis model. Through optimising the model to ascertain the enzyme distribution that would maximise light-saturated CO2 assimilation, we identified the changes in enzyme concentrations necessary to increase crop photosynthetic efficiency.
In WP2, a photosynthetically active cell-free system derived from tobacco BY-2 cells and supplemented with chloroplasts has been generated and can be used to screen and optimize chloroplast targeting efficiency of recombinant proteins. Furthermore, a protocol for highly efficient transformation of green Arabidopsis cells has been established.
In WP3, fast-track elite OXY (oxygen scavenging, strategy f) and PRB (photorespiratory bypass, strategy c) potato lines showing increased photosynthetic efficiency of 16-17% and tuber yield of 28-32% have been generated. Thus, both strategies are suitable to increase photosynthetic performance and tuber yield, and contribute to the successful achievement of milestone MS3. In addition, the WP3 partners completed the design and construction of the advanced-track multigene potato and rice transformation vectors combining the most successful strategies that will be used for potato and rice transformation in the advanced-track approach. Transformation of potato and rice plants with the final advanced-track expression vectors has been initiated.
In WP4, comprehensive physiological and photosynthetic evaluation of the new fast-track potato lines resulted on selection of promising advanced-track strategies. First elite OXY, PRB, Sp6A and VPZ potato lines are available for field trials, which will be conducted at KWS between May-October 2023.
Within WP5, a detailed biochemical characterisation has been initiated with the transgenic LR (light reaction, strategy a), OXY and PRB potato plants analysed in WP4, to evaluate the impact of multi-gene expression on the accumulation of photosynthetic end-product (glucose, fructose, sucrose, starch) as well as the primary metabolites. Further experiments are ongoing to support and strengthen our preliminary results.
For WP6, we have started focus groups consisting of stakeholders from across the rice and potato sectors in the UK and Philippines. Future workshops will involve stakeholders from another European country and one further low- or middle-income country. Although formal analysis is ongoing, several emerging themes highlight the importance of breeders choosing locally-adapted varieties when licensing future PhotoBoost improvements and optimism around new genomic techniques to provide solutions to on-farm challenges.
