Agricultural Biotechnology Research Center, Academia Sinica, Taipei 11529, Taiwan.
Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 11221, Taiwan.
Plant Physiol. 2019 Jun;180(2):813-826. doi: 10.1104/pp.19.00183. Epub 2019 Mar 21.
Mitochondrial fission occurs frequently in plant cells, but its biological significance is poorly understood because mutants specifically impaired in mitochondrial fission do not show obvious defects in vegetative growth. Here, we revealed that the production of viable pollen was reduced in mutants lacking one of the three main proteins involved in mitochondrial fission in Arabidopsis (), DYNAMIN-RELATED PROTEIN3A (DRP3A)/Arabidopsis DYNAMIN-LIKE PROTEIN2A, DRP3B, and ELONGATED MITOCHONDRIA1 (ELM1). In and , young microspores contained an abnormal number of nuclei, and mature pollen had aberrant accumulation of lipids in their coat and an irregular pollen outer wall. Because the formation of the pollen wall and coat is mainly associated with tapetal function, we used 3D imaging to quantify geometric and textural features of cells and mitochondria in the tapetum at different stages, using isolated single tapetal cells in which the in vivo morphology and volume of cells and mitochondria were preserved. Tapetal cells and their mitochondria changed in the volume and morphology at different developmental stages. Defective mitochondrial fission in the and mutants caused changes in mitochondrial status, including mitochondrial elongation, abnormal mitochondrial ultrastructure, a decrease in cross-sectional area, and a slight alteration of mitochondrial distribution, as well as a large reduction in mitochondrial density. Our studies suggest that mitochondrial fission is required for proper mitochondrial status in the tapetum and possibly in pollen as well and therefore plays an important role for the production of viable pollen.
线粒体裂变在植物细胞中经常发生，但它的生物学意义尚未被充分理解，因为专门损伤线粒体裂变的突变体在营养生长中没有明显缺陷。在这里，我们揭示了拟南芥中线粒体裂变过程中三种主要蛋白缺失之一的突变体（），动力相关蛋白 3A（DRP3A）/拟南芥动力相关蛋白样蛋白 2A、DRP3B 和伸长线粒体 1（ELM1），导致花粉活力降低。在和中，早期小孢子含有异常数量的核，成熟花粉的外壁和异常脂质积累。由于花粉壁和外壁的形成主要与绒毡层的功能有关，我们使用 3D 成像来定量分析不同阶段绒毡层细胞和线粒体的几何和纹理特征，使用分离的单个绒毡层细胞，这些细胞保留了细胞和线粒体的体内形态和体积。绒毡层细胞及其线粒体在不同发育阶段的体积和形态上发生了变化。在和突变体中，缺陷的线粒体裂变导致了线粒体状态的改变，包括线粒体伸长、异常的线粒体超微结构、横截面积减少以及线粒体分布的轻微改变，同时线粒体密度也大大降低。我们的研究表明，线粒体裂变对于绒毡层中以及可能在花粉中的线粒体状态的正常化是必需的，因此对于产生有活力的花粉起着重要作用。
