Abstract：
Endosperm, the major storage organ in cereal grains, determines the grain yield and quality. Mitochondria provide the energy for dry matter accumulation, in the endosperm development. Although mitochondrial single-stranded DNA-binding proteins (mtSSBs) play a canonical role in the maintenance of single-stranded mitochondrial DNA, their molecular functions in RNA processing and endosperm development remain obscure. Here, we report a defective rice endosperm mutant, floury endosperm26 (flo26), which develops abnormal starch grains in the endosperm. Map-based cloning and complementation experiments showed that FLO26 allele encodes a mitochondrial single-stranded DNA-binding protein, named as mtSSB1.1. Loss of function of mtSSB1.1 affects the transcriptional level of many mitochondrially-encoded genes and RNA splicing of nad1, a core component of respiratory chain complex I in mitochondria. As a result, dysfunctional mature nad1 led to dramatically decreased complex I activity, thereby reducing ATP production. Our results reveal that mtSSB1.1 plays an important role in the maintenance of mitochondrial function and endosperm development by stabilizing the splicing of mitochondrial RNA in rice.
摘要：
胚乳,谷物的主要贮藏器官，决定了粮食的产量和品质。线粒体为干物质积累提供能量，在胚乳发育中。尽管线粒体单链DNA结合蛋白（mtSSB）在维持单链线粒体DNA中起着规范作用，它们在RNA加工和胚乳发育中的分子功能仍然不清楚。这里,我们报告了一个有缺陷的水稻胚乳突变体，粉质胚乳26（flo26），在胚乳中形成异常的淀粉粒。基于图的克隆和互补实验表明，FLO26等位基因编码线粒体单链DNA结合蛋白，命名为mtSSB1.1。mtSSB1.1功能的丧失会影响许多线粒体编码基因的转录水平和nad1的RNA剪接，nad1是线粒体中呼吸链复合物I的核心成分。因此,功能失调的成熟nad1导致复合物I活性急剧下降，从而减少ATP的产生。我们的结果表明，mtSSB1.1通过稳定水稻线粒体RNA的剪接，在维持线粒体功能和胚乳发育中起重要作用。
