Light and Electron Microscopic Observations of Mitochondrial Fusion in Plasmodia Induced Sporulation in Physarum polycephalum
Light and Electron Microscopic Observations of Mitochondrial Fusion in Plasmodia Induced Sporulation in Physarum polycephalum
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多头绒泡菌疟原虫诱导孢子形成过程中线粒体融合的光镜和电镜观察
DOI：
10.1508/cytologia.52.599
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发表时间：
1987
期刊：
影响因子：
1
通讯作者：
T. Kuroiwa
中科院分区：
文献类型：
--
作者：
S. Nishibayashi;Shigeyuki Kawana;T. Kuroiwa
使用光学和电子显微镜研究了多头绒泡菌孢子形成过程中细胞核、线粒体和线粒体核的形态行为。从非营养琼脂平板上的菌核重新激活的疟原虫优先进入孢子形成。夜视摄像机和延时录像机可用于监测形态变化并确定确切的时间进程。根据形态特征，孢子形成过程分为六个阶段。孢子形成的初始事件的特征是沿着疟原虫链形成许多原生质球（原生质球阶段）。每个原生质瘤的顶端区域伸出一个乳头，伸长并变化形成茎（茎伸长阶段）。然后茎的顶端部分开始膨胀，直到达到茎伸长的最大点，然后分化为孢子囊的头部（头部膨胀阶段）。经过一个无形态变化的阶段（休眠期）后，孢子头的颜色逐渐由浅黄色变为黑色（头黑化期）。孢子囊头部完全变黑后，孢子囊完成（成熟阶段）。 4'6-二脒基-2-苯基吲哚（DAPI）落射荧光显微分光光度法显示，休眠期前菌核和饥饿胞浆体中的细胞核DNA含量与体细胞二倍体G2期细胞核相同。在休眠中期仅发生一次体细胞核分裂。减数分裂 DNA 合成发生在休眠后期和头部变黑阶段，此时细胞质裂解发生。 DNA合成后，细胞核持续处于大约一天的长G2期，并停止在减数分裂前期I。在菌核和饥饿的疟原虫中，线粒体呈球形或椭圆形，并含有一个电子致密的线粒体核（mtnucleus）。饥饿的疟原虫中线粒体和线粒体核的尺寸变小。此时每个线粒体核的DNA含量比早期饥饿的疟原虫阶段减少了一半。静息期出现哑铃状线粒体；它们有两个 mt 核，每个核分别位于哑铃形线粒体的两侧。还以低频率观察到含有 3-6 个细胞核的线粒体；多核线粒体持续到减数分裂前期I。起源于孢子的变形虫线粒体仅含有一个线粒体核。这些结果表明，线粒体核融合发生在多头绒泡菌孢子形成静止阶段的线粒体融合之后，发生在孢子萌发和阿米巴阶段之间的某个阶段。
The morphological behavior of cell nuclei, mitochondria and mitochondrial nuclei during sporulation in Physarum polycephalum was investigated using light and electron microscopy. The plasmodia which reactivated from sclerotia on non-nutrient agar plates preferentially entered into sporulation. A night vision camera and time lapse VTR were available to monitor morphological changes and determine the exact time course. Sporulation processes were classified into six stages, by morphological characteristics. The initial event of sporulation was characterized by the formation of many protoplasmic knobs along plasmodium strands (protoplasmic balling stage). A papilla was projected from the apical region of each protoplasmic knob, elongated and changed to form a stalk (stalk elongation stage). The apical part of the stalk then began to expand until it reached a maximum point of stalk elongation, thereafter differentiating into the head of the sporangium (head expanding stage). After a stage without morphological changes (resting stage), the color of the sporangial head gradually changed from pale yellow to black (head blackening stage). After full blackening of the sporangial head, sporangia were completed (mature stage). 4'6-diamidino-2-phenylindole (DAPI) epifluorescence microspectrophotometry showed that the cell nuclear DNA content in sclerotia and starved plasmodia before the resting stage was the same as that in somatic diploid G2 phase nuclei. Only a single somatic nuclear division occurred at mid-resting stage. Meiotic DNA synthesis then occurred during the late resting and head blackening stages, when cytoplasmic cleavages occurred. After DNA synthesis, cell nuclei persisted in a long G2 phase of about one day and stopped at meiotic prophase I. In sclerotia and starved plasmodia, mitochondria were spherical or oval and contained one electron-dense mitochondrial nucleus (mtnucleus). Mitochondria and mt-nucleus became smaller in size in starved plasmodia. The DNA content per mitochondrial nucleus at that time was reduced by half as compared with that at the early starved plasmodium stage. Dumbbell-shaped mitochondria appeared during the resting stage; these had two mt-nuclei, each located discretely at either side of the dumbbell-shaped mitochondrion. Mitochondria containing 3-6 nuclei were also observed, at low frequency; multinucleated mitochondria persisted up to meiotic prophase I. The mitochondria in amoebae which originated from spores contained only one mt-nucleus. These results indicate that mitochondrial nuclear fusion occurs at some stage between spore germination and the amoeba stage, following mitochondrial fusion at the resting stage of sporulation in Physarum polycephalum.