AUTHOR=Chen Zhi-Feng , Wang Tian-Hong , Feng Chao-Yang , Guo Hai-Feng , Guan Xiao-Xi , Zhang Tian-Li , Li Wen-Zhao , Xing Guo-Ming , Sun Sheng , Tan Guo-Fei 

TITLE=Multigene manipulation of photosynthetic carbon metabolism enhances the photosynthetic capacity and biomass yield of cucumber under low-CO2 environment

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.1005261

DOI=10.3389/fpls.2022.1005261

ISSN=1664-462X

ABSTRACT=<p>Solar greenhouses are important in the vegetable production and widely used for the counter-season production in the world. However, the CO<sub>2</sub> 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<sub>2</sub> 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 <italic>β-carbonic anhydrase 1</italic> (<italic>CsβCA1</italic>), <italic>β-carbonic anhydrase 4</italic> (<italic>CsβCA4</italic>), and <italic>sedoheptulose-1,7-bisphosphatase</italic> (<italic>CsSBP</italic>); <italic>fructose-1,6-bisphosphate aldolase</italic> (<italic>CsFBA</italic>), and <italic>CsβCA1</italic> co-expressing plants; <italic>CsβCA4</italic>, <italic>CsSBP</italic>, and <italic>CsFBA</italic> co-expressing plants (<italic>14SF</italic>). The results showed that the overexpression of <italic>CsβCA1</italic>, <italic>CsβCA4</italic>, <italic>and 14SF</italic> exhibited higher photosynthetic and biomass yield in transgenic cucumber plants under low-CO<sub>2</sub> environment. Further enhancements in photosynthesis and biomass yield were observed in <italic>14SF</italic> transgenic plants under low-CO<sub>2</sub> 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 <italic>CsFBA</italic> and <italic>CsSBP</italic> showed insignificant differences in photosynthesis and biomass yield compared with the WT under low-CO<sub>2</sub>.environment. Photosynthesis, fluorescence parameters, and enzymatic measurements indicated that <italic>CsβCA1</italic>, <italic>CsβCA4</italic>, <italic>CsSBP</italic>, and <italic>CsFBA</italic> had cumulative effects in photosynthetic carbon assimilation under low-CO<sub>2</sub> environment. Co-expression of this four genes (<italic>CsβCA1</italic>, <italic>CsβCA4</italic>, <italic>CsSBP</italic>, and <italic>CsFBA</italic>) can increase the carboxylation activity of RuBisCO and promote the regeneration of RuBP. As a result, the <italic>14SF</italic> transgenic plants showed a higher net photosynthetic rate and biomass yield even under low-CO<sub>2</sub>environment.These findings demonstrate the possibility of cultivating crops with high photosynthetic efficiency by manipulating genes involved in the photosynthetic carbon assimilation metabolic pathway.</p>