Key Laboratory of Rice Biology and Genetic Breeding in Northeast China (Ministry of Agriculture and Rural Areas), Rice Research Institute of Shenyang Agricultural University, Shenyang, 110866, People's Republic of China.
Planta. 2023 Mar 9;257(4):77. doi: 10.1007/s00425-023-04109-z.
GRA117 is crucial in the process of carbon assimilation in rice as it regulates the development of chloroplasts, which in turn facilitates the Calvin-Benson cycle. Carbon assimilation is a critical process for plant growth, and despite numerous relevant studies, there are still unknown constraints. In this study, we isolated a rice mutant, gra117, which exhibited seedling albinism, delayed chloroplast development, decreased chlorophyll content, reduced yield, and seedling stress susceptibility, as compared to WT. Our further investigations revealed that gra117 had a significantly lower net photosynthetic carbon assimilation rate, as well as reduced levels of Rubisco enzyme activity, RUBP, PGA, carbohydrate, protein content, and dry matter accumulation. These findings provide evidence for decreased carbon assimilation in gra117. By mapping cloning, we discovered a 665 bp insertion in the GRA117 promoter region that decreases GRA117 transcriptional activity and causes the gra117 phenotype. GRA117 encodes PfkB-type fructokinase-like 2, which is subcellularly localized in chloroplasts and is widely expressed in various rice tissues, particularly at high levels in leaf tissues. GRA117 transcription is regulated by the core region 1029 bp before the start codon. Our quantitative RT-PCR and Western blot assays showed that GRA117 promotes the expression and translation of photosynthetic genes. RNA-Seq analysis revealed that GRA117 plays a significant role in photosynthetic carbon fixation, carbon metabolism, and chloroplast ribosome-related pathways. Our study supports that GRA117 promotes the Calvin-Benson cycle by regulating chloroplast development, ultimately leading to enhanced carbon assimilation in rice.
GRAl17 在水稻的碳同化过程中至关重要，因为它调节叶绿体的发育，而叶绿体又促进卡尔文-本森循环。碳同化是植物生长的关键过程，尽管有许多相关研究，但仍有未知的限制。在这项研究中，我们分离出一个水稻突变体 gra117，与 WT 相比，该突变体表现为幼苗白化、叶绿体发育延迟、叶绿素含量降低、产量降低和幼苗对胁迫的敏感性增加。我们进一步的研究表明，gra117 的净光合碳同化率显著降低，Rubisco 酶活性、RUBP、PGA、碳水化合物、蛋白质含量和干物质积累减少。这些发现为 gra117 中碳同化减少提供了证据。通过图谱克隆，我们发现 GRA117 启动子区域有一个 665bp 的插入，降低了 GRA117 的转录活性，并导致 gra117 表型。GRA117 编码 PfkB 型果糖激酶样 2，它在亚细胞水平上定位于叶绿体中，在各种水稻组织中广泛表达，特别是在叶片组织中表达水平较高。GRA117 的转录受起始密码子前 1029bp 的核心区域调控。我们的定量 RT-PCR 和 Western blot 分析表明，GRA117 促进了光合作用基因的表达和翻译。RNA-Seq 分析表明，GRA117 在光合作用碳固定、碳代谢和叶绿体核糖体相关途径中起着重要作用。我们的研究支持 GRA117 通过调节叶绿体发育来促进卡尔文-本森循环，最终导致水稻中碳同化的增强。
