STUDIES ON THE BEHAVIOR OF ORGANELLES AND THEIR NUCLEOIDS IN THE ROOT APICAL MERISTEM OF ARABIDOPSIS-THALIANA (L) COL
STUDIES ON THE BEHAVIOR OF ORGANELLES AND THEIR NUCLEOIDS IN THE ROOT APICAL MERISTEM OF ARABIDOPSIS-THALIANA (L) COL
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DOI：
10.1007/bf00194444
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发表时间：
1993-03-01
期刊：
影响因子：
4.3
通讯作者：
KUROIWA, T
中科院分区：
文献类型：
--
作者：
FUJIE, M;KUROIWA, H;KUROIWA, T
研究了拟南芥根尖分生组织中细胞核、线粒体类核(mt-核)和质体类核(pt-核)的行为。样品包埋在Technovit 7100树脂中，切成薄片，4‘-6-二氨基-2-苯基吲哚染色，进行光镜放射自显影和显微分光光度测定。在距中央细胞0~300um的根尖分生组织中，细胞核DNA的合成和细胞分裂都很活跃。据估计，根尖分生组织下部产生的细胞经过至少四次分裂后进入伸长区。在整个分生组织带中，单个细胞都有线粒体，其中含有1-5个线粒体核团。中央圆柱体分生组织中线粒体数量由65个逐渐增加到200个。因此，在整个分生组织中，单个线粒体在每个有丝分裂周期中分裂一次或两次。相反，基于[H-3]胸腺嘧啶核苷掺入细胞器类核，线粒体DNA(MtDNA)和质体DNA(PtDNA)的合成独立于有丝分裂周期，主要在一个限制区域(即根尖分生组织的下部)发生。利用视频增强的显微镜光子计数系统进行的荧光测量显示，在分生组织下部的细胞中，mtDNA合成活跃的细胞中每个mt-核的mtDNA数量对应于1MBP以上。相比之下，在根尖伸长区正下方的分生组织细胞中，每个mt-核的mtDNA数量下降到大约170kBP。这些发现有力地表明，在低水平的mtDNA合成过程中，由于线粒体的持续分裂，在分生组织的下部合成的每个线粒体的mtDNA数量逐渐减少。这一现象可以解释为什么延伸区的分化细胞的线粒体只含有极少量的mtDNA。
The behavior of cell nuclei, mitochondrial nucleoids (mt-nucleoids) and plastid nucleoids (pt-nucleoids) was studied in the root apical meristem of Arabidopsis thaliana. Samples were embedded in Technovit 7100 resin, cut into thin sections and stained with 4'-6-diamidino-2-phenylindole for light-microscopic autoradiography and microphotometry. Synthesis of cell nuclear DNA and cell division were both active in the root apical meristem between 0 mum and 300 mum from the central cells. It is estimated that the cells generated in the lower part of the root apical meristem enter the elongation zone after at least four divisions. Throughout the entire meristematic zone, individual cells had mitochondria which contained 1-5 mt-nucleoids. The number of mitochondria increased gradually from 65 to 200 in the meristem of the central cylinder. Therefore, throughout the meristem, individual mitochondria divided either once or twice per mitotic cycle. By contrast, based on the incorporation of [H-3]thymidine into organelle nucleoids, syntheses of mitochondrial DNA (mtDNA) and plastid DNA (ptDNA) occurred independently of the mitotic cycle and mainly in a restricted region (i.e., the lower part of the root apical meristem). Fluorimetry, using a video-intensified microscope photon-counting system, revealed that the amount of mtDNA per mt-nucleoid in the cells in the lower part of the meristem, where mtDNA synthesis was active, corresponded to more than 1 Mbp. By contrast, in the meristematic cells just below the elongation zone of the root tip, the amount of mtDNA per mt-nucleoid fell to approximately 170 kbp. These findings strongly indicate that the amount of mtDNA per mitochondrion, which has been synthesized in the lower part of the meristem, is gradually reduced as a result of continual mitochondrial divisions during low levels of mtDNA synthesis. This phenomenon would explain why differentiated cells in the elongation zone have mitochondria that contain only extremely small amounts of mtDNA.