To ensure efficient photosynthesis, chloroplast proteins need to be flexibly regulated under fluctuating light conditions. Thiol-based redox regulation plays a key role in reductively activating several chloroplast proteins in a light-dependent manner. The ferredoxin (Fd)/thioredoxin (Trx) pathway has long been recognized as the machinery that transfers reducing power generated by photosynthetic electron transport reactions to redox-sensitive target proteins; however, its biological importance remains unclear, because the complete disruption of the Fd/Trx pathway in plants has been unsuccessful to date. Especially, recent identifications of multiple redox-related factors in chloroplasts, as represented by the NADPH–Trx reductase C, have raised a controversial proposal that other redox pathways work redundantly with the Fd/Trx pathway. To address these issues directly, we used CRISPR/Cas9 gene editing to create Arabidopsis mutant plants in which the activity of the Fd/Trx pathway was completely defective. The mutants generated showed severe growth inhibition. Importantly, these mutants almost entirely lost the ability to reduce several redox-sensitive proteins in chloroplast stroma, including four Calvin–Benson cycle enzymes, NADP–malate dehydrogenase, and Rubisco activase, under light conditions. These striking phenotypes were further accompanied by abnormally developed chloroplasts and a drastic decline in photosynthetic efficiency. These results indicate that the Fd/Trx pathway is indispensable for the light-responsive activation of diverse stromal proteins and photoautotrophic growth of plants. Our data also suggest that the ATP synthase is exceptionally reduced by other pathways in a redundant manner. This study provides an important insight into how the chloroplast redox-regulatory system operates in vivo.

为了确保有效的光合作用，需要在波动的光照条件下灵活调节叶绿体蛋白。基于硫醇的氧化还原调节在以光依赖性方式还原激活几种叶绿体蛋白方面起着关键作用。长期以来，铁氧还蛋白 (Fd)/硫氧还蛋白 (Trx) 途径被认为是将光合电子传递反应产生的还原力传递给氧化还原敏感靶蛋白的机制；然而，其生物学重要性仍不清楚，因为迄今为止，完全破坏植物中的 Fd/Trx 通路尚未成功。特别是，最近对叶绿体中多种氧化还原相关因子的鉴定，以 NADPH-Trx 还原酶 C 为代表，提出了一个有争议的提议，即其他氧化还原途径与 Fd/Trx 途径冗余工作。拟南芥Fd/Trx 通路活性完全缺陷的突变植物。产生的突变体表现出严重的生长抑制。重要的是，这些突变体几乎完全丧失了在光照条件下减少叶绿体基质中几种氧化还原敏感蛋白的能力，包括四种 Calvin-Benson 循环酶、NADP-苹果酸脱氢酶和 Rubisco 激活酶。这些显着的表型进一步伴随着异常发育的叶绿体和光合效率的急剧下降。这些结果表明，Fd/Trx 通路对于不同基质蛋白的光响应激活和植物的光合自养生长是必不可少的。我们的数据还表明，ATP 合酶以冗余方式被其他途径异常减少。体内。