Several photorespiratory bypasses have been introduced into plants and shown to improve photosynthesis by increasing chloroplastic CO₂ concentrations or optimizing energy balance. We recently reported that an engineered GOC bypass could increase photosynthesis and productivity in rice. However, the grain yield of GOC plants was unstable, fluctuating in different cultivation seasons because of varying seed setting rates. In this study, we designed a synthetic photorespiratory shortcut (the GCGT bypass) consisting of genes encoding Oryza sativa glycolate oxidase and Escherichia coli catalase, glyoxylate carboligase, and tartronic semialdehyde reductase. The GCGT bypass was guided by an optimized chloroplast transit peptide that targeted rice chloroplasts and redirected 75% of carbon from glycolate metabolism to the Calvin cycle, identical to the native photorespiration pathway. GCGT transgenic plants exhibited significantly increased biomass production and grain yield, which were mainly attributed to enhanced photosynthesis due to increased chloroplastic CO₂ concentrations. Despite the increases in biomass production and grain yield, GCGT transgenic plants showed a reduced seed setting rate, a phenotype previously reported for the GOC plants. Integrative transcriptomic, physiological, and biochemical assays revealed that photosynthetic carbohydrates were not transported to grains in an efficient manner, thereby reducing the seed setting rate. Taken together, our results demonstrate that the GCGT photorespiratory shortcut confers higher yield by promoting photosynthesis in rice, mainly through increasing chloroplastic CO₂ concentrations.

几种光呼吸旁路已被引入植物中，并显示出通过增加叶绿体CO ₂浓度或优化能量平衡来改善光合作用。我们最近报道说，设计的GOC旁路可以提高水稻的光合作用和生产力。然而，由于结实率的变化，GOC植物的谷物产量不稳定，在不同的栽培季节中波动。在这项研究中，我们设计了合成的光呼吸快捷方式（在GCGT旁路）由基因编码水稻乙醇酸氧化酶和大肠杆菌过氧化氢酶，乙醛酸羧化酶和tartronic半醛还原酶。GCGT旁路由优化的叶绿体转运肽引导，该肽靶向水稻的叶绿体并将乙醇酸代谢的75％的碳重定向到加尔文循环，与天然光呼吸途径相同。GCGT转基因植物的生物量产量和谷物产量均显着增加，这主要归因于叶绿体CO ₂含量增加导致光合作用增强浓度。尽管增加了生物量产量和谷物产量，GCGT转基因植物的结实率却降低了，这是以前报道的GOC植物的表型。综合转录组学，生理和生化分析表明，光合碳水化合物没有以有效的方式转运到谷物，从而降低了结实率。两者合计，我们的结果表明，GCGT光呼吸捷径主要通过增加叶绿体CO ₂浓度来促进水稻的光合作用，从而提高产量。