In the third year of the Photoboost project significant progress was made towards the project’s final goals. Adaptation of metabolic models improved the understanding of the role of different key enzymes as targets for further optimization to boost photosynthetic yields. Initial results from fast-track potato lines grown in the greenhouse, show increased photosynthetic efficiency and yield improvements of up to 44%. Based on these results field trials for fast track potato lines as well as cloning of advanced track constructs for potato and rice transformation were initiated. Taken together these results demonstrate that the project is on an excellent way to reach its initial goal of developing and implementing strategies to boost the productivity and performance of essential crops like potatoes and rice. A more detailed description of the results that were generated in the context of the different work packages can be found below.
WP1: In work package 1, 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.
WP2: The cell-free system derived from tobacco BY-2 cells and supplemented with chloroplasts has been further optimised and protocol for highly efficient transformation of green Arabidopsis cells could be established.
WP3: Fast-track elite OXY (oxygen scavenging, strategy f) and PRB (photorespiratory bypass, strategy c) potato lines showing increased photosynthetic efficiency (OXY up to 27% and PRB up to 22%) and tuber yield of 29 (OXY) and 44% (PRB) have been generated. Thus, both strategies are suitable to increase photosynthetic performance and tuber yield. In rice, up to 46% increase in the photosynthetic efficiency at dough stage was achieved by expression of LCIB alone, one of the components of the CCM strategy, and up 19% increase was obtained with the combination of the strategies LR + OXY.
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.
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 (strategy d) and VPZ potato lines are available for field trials, which will be conducted at KWS later in 2023.
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.
WP6: As part of work package 6, we have started focus groups consisting of stakeholders from across the rice and potato sectors in the UK and the 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.