Multigene manipulation of photosynthetic carbon metabolism enhances the photosynthetic capacity and biomass yield of cucumber under low-CO environment.

Solar greenhouses are important in the vegetable production and widely used for the counter-season production in the world. However, the CO consumed by crops for photosynthesis after sunrise is not supplemented and becomes chronically deficient due to the airtight structure of solar greenhouses. Vegetable crops cannot effectively utilize light resources under low-CO environment, and this incapability results in reduced photosynthetic efficiency and crop yield. We used cucumber as a model plant and generated several sets of transgenic cucumber plants overexpressing individual genes, including (), (), and (); (), and co-expressing plants; , , and co-expressing plants (). The results showed that the overexpression of , , exhibited higher photosynthetic and biomass yield in transgenic cucumber plants under low-CO environment. Further enhancements in photosynthesis and biomass yield were observed in transgenic plants under low-CO environment. The net photosynthesis biomass yield and photosynthetic rate increased by 49% and 79% compared with those of the WT. However, the transgenic cucumbers of overexpressing and showed insignificant differences in photosynthesis and biomass yield compared with the WT under low-CO.environment. Photosynthesis, fluorescence parameters, and enzymatic measurements indicated that , , , and had cumulative effects in photosynthetic carbon assimilation under low-CO environment. Co-expression of this four genes (, , , and ) can increase the carboxylation activity of RuBisCO and promote the regeneration of RuBP. As a result, the transgenic plants showed a higher net photosynthetic rate and biomass yield even under low-COenvironment.These findings demonstrate the possibility of cultivating crops with high photosynthetic efficiency by manipulating genes involved in the photosynthetic carbon assimilation metabolic pathway.