Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan, 250100, China.
New Phytol. 2019 Jan;221(2):896-907. doi: 10.1111/nph.15425. Epub 2018 Aug 31.
RNA editing plays an important role in organellar gene expression in plants, and pentatricopeptide repeat (PPR) proteins are involved in this function. Because of its large family size, many PPR proteins are not known for their function and roles in plant growth and development. Through genetic and molecular analyses of the empty pericarp18 (emp18) mutant in maize (Zea mays), we cloned the Emp18 gene, revealed its molecular function, and defined its role in the mitochondrial complex assembly and seed development. Emp18 encodes a mitochondrial-localized DYW-PPR protein. Null mutation of Emp18 arrests embryo and endosperm development at an early stage in maize, resulting in embryo lethality. Mutants are deficient in the cytidine (C)-to-uridine (U) editing at atp6-635 and cox2-449, which converts a Leu to Pro in ATP6 and a Met to Thr in Cox2. The atp6 gene encodes the subunit a of F F -ATPase. The Leu to Pro alteration disrupts an α-helix of subunit a, resulting in a dramatic reduction in assembly and activity of F F -ATPase holoenzyme and an accumulation of free F -subcomplex. These results demonstrate that EMP18 functions in the C-to-U editing of atp6 and cox2, and is essential to mitochondrial biogenesis and seed development in maize.
RNA 编辑在植物细胞器基因表达中发挥重要作用，而五肽重复（PPR）蛋白参与了这一功能。由于其庞大的家族规模，许多 PPR 蛋白的功能及其在植物生长发育中的作用尚不清楚。通过对玉米（Zea mays）空果皮 18（emp18）突变体的遗传和分子分析，我们克隆了 Emp18 基因，揭示了其分子功能，并定义了其在线粒体复合物组装和种子发育中的作用。Emp18 编码一种定位于线粒体的 DYW-PPR 蛋白。玉米中 Emp18 的无效突变会在早期阻止胚胎和胚乳的发育，导致胚胎致死。突变体在 atp6-635 和 cox2-449 处的胞嘧啶（C）到尿嘧啶（U）编辑缺失，这将导致 ATP6 中的亮氨酸到脯氨酸和 Cox2 中的蛋氨酸到苏氨酸的转换。atp6 基因编码 FF-ATP 酶的亚基 a。亮氨酸到脯氨酸的改变破坏了亚基 a 的一个α-螺旋，导致 FF-ATP 酶全酶的组装和活性显著降低，以及游离 F-亚基的积累。这些结果表明 EMP18 在线粒体基因的 C 到 U 编辑中发挥作用，对玉米线粒体生物发生和种子发育至关重要。
