Chlorophyll is one of the key factors for photosynthesis and plays an important role in plant growth and development. We previously isolated an EMS mutagenized rapeseed chlorophyll-reduced mutant (crm1), which had yellow leaf, reduced chlorophyll content and fewer thylakoid stacks. Here, we found that crm1 showed attenuated utilization efficiency of both light energy and CO₂ but enhanced heat dissipation efficiency and greater tolerance to high-light intensity. BSA-Seq analysis identified a single nucleotide change (C to T) and (G to A) in the third exon of the BnaA01G0094500ZS and BnaC01G0116100ZS, respectively. These two genes encode the magnesium chelatase subunit I 1 (CHLI1) that catalyzes the insertion of magnesium into protoporphyrin IX, a pivotal step in chlorophyll synthesis. The mutation sites resulted in an amino acid substitution P144S and G128E within the AAA+ domain of the CHLI1 protein. Two KASP markers were developed and co-segregated with the yellow leaf phenotype in segregating F₂ population. Loss of BnaA01.CHLI1 and BnaC01.CHLI1 by CRISPR/Cas9 gene editing recapitulated the mutant phenotype. BnaA01.CHLI1 and BnaC01.CHLI1 were located in chloroplast and highly expressed in the leaves. Furthermore, RNA-seq analyses revealed the expression of chlorophyll synthesis–related genes were upregulated in the crm1 mutant. These findings provide a new insight into the regulatory mechanism of chlorophyll synthesis in rapeseed and suggest a novel target for improving the photosynthetic efficiency and tolerance to high-light intensity in crops.

叶绿素是光合作用的关键因子之一，在植物生长发育中发挥着重要作用。我们之前分离出一个EMS诱变的油菜叶绿素减少突变体（crm1），该突变体具有黄叶、叶绿素含量降低和类囊体堆积较少。在这里，我们发现crm1表现出光能和CO ₂的利用效率减弱，但散热效率增强并且对高光强度的耐受性更强。BSA-Seq 分析分别鉴定了BnaA01G0094500ZS和BnaC01G0116100ZS的第三个外显子中的单核苷酸变化（C 至 T）和（G 至 A）。这两个基因编码镁螯合酶亚基 I 1 (CHLI1)，可催化镁插入原卟啉 IX，这是叶绿素合成的关键步骤。突变位点导致 CHLI1 蛋白 AAA+ 结构域内的氨基酸取代 P144S 和 G128E。_{开发了两个 KASP 标记，并在分离 F 2}群体中与黄叶表型共分离。CRISPR/Cas9 基因编辑导致BnaA01.CHLI1和BnaC01.CHLI1的丢失重现了突变表型。BnaA01.CHLI1和BnaC01.CHLI1位于叶绿体中，在叶片中高表达。此外，RNA-seq 分析显示crm1突变体中叶绿素合成相关基因的表达上调。这些发现为油菜籽叶绿素合成的调控机制提供了新的见解，并为提高作物光合效率和高光强度耐受性提出了新的目标。