Horticultural Sciences Department, University of Florida, Gainesville, FL, 32611-0690, USA.
Emergency Department, Baton Rouge General Medical Center, Baton Rouge, LA, 70809, USA.
BMC Plant Biol. 2022 Nov 1;22(1):508. doi: 10.1186/s12870-022-03897-y.
Cytoplasmic male sterility (CMS) is a maternally inherited failure to produce functional pollen that most commonly results from expression of novel, chimeric mitochondrial genes. In Zea mays, cytoplasmic male sterility type S (CMS-S) is characterized by the collapse of immature, bi-cellular pollen. Molecular and cellular features of developing CMS-S and normal (N) cytoplasm pollen were compared to determine the role of mitochondria in these differing developmental fates.
Terminal deoxynucleotidyl transferase dUTP nick end labeling revealed both chromatin and nuclear fragmentation in the collapsed CMS-S pollen, demonstrating a programmed cell death (PCD) event sharing morphological features with mitochondria-signaled apoptosis in animals. Maize plants expressing mitochondria-targeted green fluorescent protein (GFP) demonstrated dynamic changes in mitochondrial morphology and association with actin filaments through the course of N-cytoplasm pollen development, whereas mitochondrial targeting of GFP was lost and actin filaments were disorganized in developing CMS-S pollen. Immunoblotting revealed significant developmental regulation of mitochondrial biogenesis in both CMS-S and N mito-types. Nuclear and mitochondrial genome encoded components of the cytochrome respiratory pathway and ATP synthase were of low abundance at the microspore stage, but microspores accumulated abundant nuclear-encoded alternative oxidase (AOX). Cytochrome pathway and ATP synthase components accumulated whereas AOX levels declined during the maturation of N bi-cellular pollen. Increased abundance of cytochrome pathway components and declining AOX also characterized collapsed CMS-S pollen. The accumulation and robust RNA editing of mitochondrial transcripts implicated translational or post-translational control for the developmentally regulated accumulation of mitochondria-encoded proteins in both mito-types.
CMS-S pollen collapse is a PCD event coincident with developmentally programmed mitochondrial events including the accumulation of mitochondrial respiratory proteins and declining protection against mitochondrial generation of reactive oxygen species.
细胞质雄性不育（CMS）是一种母系遗传的花粉功能丧失，最常见于新型嵌合线粒体基因的表达。在玉米中，细胞质雄性不育类型 S（CMS-S）的特征是未成熟的双细胞花粉崩溃。比较了发育中的 CMS-S 和正常（N）细胞质花粉的分子和细胞特征，以确定线粒体在这些不同发育命运中的作用。
末端脱氧核苷酸转移酶 dUTP 缺口末端标记显示在崩溃的 CMS-S 花粉中染色质和核片段化，表明程序化细胞死亡（PCD）事件与动物中线粒体信号诱导的细胞凋亡具有形态特征。表达线粒体靶向绿色荧光蛋白（GFP）的玉米植株在 N 细胞质花粉发育过程中显示出线粒体形态的动态变化，并与肌动蛋白丝相关联，而 GFP 靶向线粒体的丢失和肌动蛋白丝的紊乱发生在发育中的 CMS-S 花粉中。免疫印迹显示 CMS-S 和 N 线粒体类型中线粒体生物发生的显著发育调控。核和线粒体基因组编码的细胞色素呼吸途径和 ATP 合酶成分在小孢子阶段含量低，但小孢子积累了丰富的核编码替代氧化酶（AOX）。在 N 双细胞花粉的成熟过程中，细胞色素途径成分积累，而 AOX 水平下降。崩溃的 CMS-S 花粉也表现出细胞色素途径成分的丰度增加和 AOX 的下降。线粒体转录物的积累和强大的 RNA 编辑暗示了翻译或翻译后控制对于两种线粒体类型中线粒体编码蛋白的发育调控积累。
CMS-S 花粉崩溃是与发育程序控制的线粒体事件同时发生的 PCD 事件，包括线粒体呼吸蛋白的积累和对线粒体产生的活性氧的保护下降。
