Insertion of photorespiratory bypasses in Physcomitrium patens to improve carbon usage efficiency

Since 1950, world population have been strongly growing leading to a corresponding increase in food demand. Genetic selection and agricultural improvements supported this growth strongly improving agricultural productivity. Population is expected to continue growing, calling for the necessity of innovative strategies to improve productivity. One promising possibility is to improve photosynthetic efficiency and thus biomass productivity targeting photorespiration, an indispensable but extremely energy-demanding process. This research aims to substitute, in Physcomitrium patens, the native photorespiration with two alternative pathways which do not cause carbon and nitrogen losses, thus potentially resulting in larger biomass productivities: the marine proteobacteria ß-Hydroxy-Aspartate Cycle (BHAC) and the synthetically designed Tartronyl-CoA (TaCo) pathway. The model organism Physcomitrium patens was selected for this test for its rapidity in genetic manipulation and for an haploid phase predominance in its life cycle which make testing of genetic modifications faster than in crops. Genomic and physiological screening analysis, identified clones with a stable integration of BHAC genes in both wild-type and a plgg1 Knock-out line with photorespiratory impaired phenotype. Physiological analyses were performed to characterize some of the obtained lines demonstrating the impact of BHAC pathway activity and suggesting this strategy is indeed effective in improving photosynthetic efficiency.