Sun Hu, Schmidt Nils, Lawson Tracy, Hagemann Martin, Timm Stefan
Plant Physiology Department, University of Rostock, Albert-Einstein-Straße 3, D-18059, Rostock, Germany.
University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK.
New Phytol. 2025 Jun;246(5):2102-2117. doi: 10.1111/nph.70124. Epub 2025 Apr 11.
Photorespiration is a mandatory metabolic repair shunt of carbon fixation by the Calvin-Benson cycle in oxygenic phototrophs. Its extent depends mainly on the CO : O ratio in chloroplasts, which is regulated via stomatal movements. Despite a comprehensive understanding of the role of photorespiration in mesophyll cells, its role in guard cells (GC) is unknown. Therefore, a key enzyme of photorespiration, glycine decarboxylase (GDC), was specifically manipulated by varying glycine decarboxylase H-protein (GDC-H) expression in Arabidopsis GC. Multiple approaches were used to analyze the transgenic lines growth, their gas exchange and Chl fluorescence, alongside metabolomics and microscopic approaches. We observed a positive correlation of GC GDC-H expression with growth, photosynthesis and carbohydrate biosynthesis, suggesting photorespiration is involved in stomatal regulation. Gas exchange measurements support this view, as optimized GC photorespiration improved plant acclimation toward conditions requiring a high photorespiratory capacity. Microscopic analysis revealed that altered photorespiratory flux also affected GC starch accumulation patterns, eventually serving as an underlying mechanism for altered stomatal behavior. Collectively, our data suggest photorespiration is involved in the regulatory circuit that coordinates stomatal movements with CO availability. Thus, the manipulation of photorespiration in GC has the potential to engineer crops maintaining growth and photosynthesis under future climates.
光呼吸是光合自养生物中卡尔文-本森循环固定碳的一种强制性代谢修复旁路。其程度主要取决于叶绿体中的CO₂:O₂比率，该比率通过气孔运动进行调节。尽管对光呼吸在叶肉细胞中的作用有全面的了解，但其在保卫细胞（GC）中的作用尚不清楚。因此，通过改变拟南芥保卫细胞中甘氨酸脱羧酶H蛋白（GDC-H）的表达，特异性地操纵了光呼吸的关键酶甘氨酸脱羧酶（GDC）。采用多种方法分析转基因株系的生长、气体交换和叶绿素荧光，同时结合代谢组学和显微镜方法。我们观察到保卫细胞GDC-H表达与生长、光合作用和碳水化合物生物合成呈正相关，这表明光呼吸参与气孔调节。气体交换测量结果支持这一观点，因为优化的保卫细胞光呼吸改善了植物对需要高光呼吸能力条件的适应性。显微镜分析表明，改变的光呼吸通量也影响保卫细胞淀粉积累模式，最终成为气孔行为改变的潜在机制。总体而言，我们的数据表明光呼吸参与了将气孔运动与CO₂可用性相协调的调节回路。因此，操纵保卫细胞中的光呼吸有可能培育出在未来气候条件下保持生长和光合作用的作物。
