Chen Guoxin, Li Yanni, Jin Kaining, Gao Jiabei, Wu Suting, Cui Xuean, Mao Chuanzao, Yin Xinyou, Lu Tiegang, Zhang Zhiguo
Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, P. R. China.
Department of Plant Sciences, Centre for Crop Systems Analysis, Wageningen University & Research, 6700 AK Wageningen, The Netherlands.
Plant Cell. 2024 Dec 23;37(1). doi: 10.1093/plcell/koaf015.
Photorespiration, often considered as a wasteful process, is a key target for bioengineering to improve crop yields. Several photorespiratory bypasses have been designed to efficiently metabolize 2-phosphoglycolate and increase the CO2 concentration in chloroplasts, thereby reducing photorespiration. However, the suppression of primary nitrate assimilation remains an issue when photorespiration is inhibited. In this study, we designed a carbon and nitrogen metabolism-coupled photorespiratory bypass, termed the GCBG bypass, in rice (Oryza sativa) chloroplasts. Our results demonstrated efficient assembly and expression of the GCBG bypass in rice chloroplasts, which affected the levels of typical metabolites and their derivatives of natural photorespiration and enhanced the photosynthetic efficiency. Metabolomic analyses revealed that oxaloacetate, produced from glycolate in chloroplasts, positively impacted amino acid synthesis, energy metabolism, and sugar synthesis. The engineered GCBG plants showed an average yield increase of 19.0% (17.8% to 20.2%) compared with wild-type plants under natural growth conditions, alongside improved nitrogen uptake, which compensated for 44.1% of yield losses under nitrogen-limited conditions. In summary, the GCBG bypass substantially improved the photosynthetic efficiency, biomass, and yield in rice by integrating carbon and nitrogen metabolism. This study introduces a strategy for engineering high-yielding rice or other crops with improved photosynthetic efficiency and nitrogen uptake.
光呼吸通常被认为是一个浪费的过程，是生物工程提高作物产量的关键目标。已经设计了几种光呼吸支路来有效代谢2-磷酸乙醇酸并提高叶绿体中的二氧化碳浓度，从而减少光呼吸。然而，当光呼吸受到抑制时，初级硝酸盐同化的抑制仍然是一个问题。在本研究中，我们在水稻（Oryza sativa）叶绿体中设计了一种碳氮代谢偶联的光呼吸支路，称为GCBG支路。我们的结果表明，GCBG支路在水稻叶绿体中有效组装和表达，影响了天然光呼吸的典型代谢物及其衍生物的水平，并提高了光合效率。代谢组学分析表明，叶绿体中由乙醇酸产生的草酰乙酸对氨基酸合成、能量代谢和糖合成产生积极影响。在自然生长条件下，与野生型植物相比，经过基因工程改造的GCBG植物平均产量提高了19.0%（17.8%至20.2%），同时氮吸收得到改善，这补偿了氮限制条件下44.1%的产量损失。总之，GCBG支路通过整合碳氮代谢，显著提高了水稻的光合效率、生物量和产量。本研究介绍了一种培育具有提高光合效率和氮吸收能力的高产水稻或其他作物的策略。
