Wang Yong, Liu Xin-Yuan, Huang Zi-Qin, Li Yan-Yan, Yang Yan-Zhuo, Sayyed Aqib, Sun Feng, Gu Zhi-Qun, Wang Xiaomin, Tan Bao-Cai
Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, China.
Key Laboratory of Cell Activities and Stress Adaptations, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou, China.
Front Plant Sci. 2021 Jul 28;12:693272. doi: 10.3389/fpls.2021.693272. eCollection 2021.
The conversion of cytidines to uridines (C-to-U) at specific sites in mitochondrial and plastid transcripts is a post-transcriptional processing event that is important to the expression of organellar genes. Pentatricopeptide repeat (PPR) proteins are involved in this process. In this study, we report the function of a previously uncharacterized PPR-DYW protein, Empty pericarp17 (EMP17), in the C-to-U editing and kernel development in maize. EMP17 is targeted to mitochondria. The loss-function of EMP17 arrests maize kernel development, abolishes the editing at -799 and -677 sites, and reduces the editing at -906 and -966 sites. The absence of editing causes amino acid residue changes in CcmF-267 (Ser to Pro) and Nad2-226 (Phe to Ser), respectively. As CcmF functions in cytochrome (Cyt) maturation, the amount of Cyt and Cyt protein is drastically reduced in , suggesting that the CcmF-267 (Ser to Pro) change impairs the CcmF function. As a result, the assembly of complex III is strikingly decreased in . In contrast, the assembly of complex I appears less affected, suggesting that the Nad2-226 (Phe to Ser) change may have less impact on Nad2 function. Together, these results indicate that EMP17 is required for the C-to-U editing at several sites in mitochondrial transcripts, complex III biogenesis, and seed development in maize.
胞嘧啶核苷在线粒体和质体转录本特定位点向尿嘧啶核苷的转变（C-to-U）是一种对细胞器基因表达很重要的转录后加工事件。五肽重复（PPR）蛋白参与了这一过程。在本研究中，我们报道了一种之前未被鉴定的PPR-DYW蛋白——空颖果17（EMP17）在玉米C-to-U编辑和籽粒发育中的功能。EMP17定位于线粒体。EMP17功能缺失会使玉米籽粒发育停滞，消除-799和-677位点的编辑，并减少-906和-966位点的编辑。编辑缺失分别导致CcmF-267（丝氨酸变为脯氨酸）和Nad2-226（苯丙氨酸变为丝氨酸）的氨基酸残基发生变化。由于CcmF在细胞色素（Cyt）成熟过程中发挥作用，在EMP17功能缺失突变体中Cyt和Cyt蛋白的量大幅减少，这表明CcmF-267（丝氨酸变为脯氨酸）的变化损害了CcmF的功能。结果，在EMP17功能缺失突变体中复合物III的组装显著减少。相比之下，复合物I的组装受影响较小，这表明Nad2-226（苯丙氨酸变为丝氨酸）的变化对Nad2功能的影响可能较小。总之，这些结果表明EMP17是玉米线粒体转录本中几个位点的C-to-U编辑、复合物III生物合成和种子发育所必需的。
