Behavior of organelles and their nucleoids in the shoot apical meristem during leaf development in Arabidopsis thaliana L
1994
Fujie, M. | Kuroiwa, H. | Kawano, S. | Mutoh, S. | Kuroiwa, T.
The behavior of organelle nucleoids and cell nuclei was studied in the shoot apical meristem and developing first foliage leaves of Arabidopsis thaliana. Samples were embedded in Technovit 7100 resin, cut into thin sections and stained with 4'-6-diamidino-2-phenylindole to observe DNA. Fluorimetry was performed using a video-intensified microscope photon-counting system. The DNA content of individual mitochondria was more than 1 Mbp in the shoot apical meristem and the young leaf primordium, and decreased to approximately 170 kbp in the mature foliage leaf. In contrast, the DNA content of individual plastics was low in the shoot apical meristem and increased until day 7 after sowing. Application of 5-bromo-2'-deoxyuridine, an analogue of thymidine, was used to investigate DNA synthesis in situ. The activities of DNA synthesis in the mitochondria and plastics changed according to the stage of development. Mitochondrial DNA was actively synthesized in the shoot apical meristem and young leaf primordia. This strongly suggests that the amount of mitochondrial DNA per mitochondrion, which has been synthesized in the shoot apical meristem and young leaf primordium, is gradually reduced due to continual divisions of the mitochondria during low levels of mitochondrial DNA synthesis. Synthesis of DNA in the plastic became active in the leaf primordia following DNA synthesis in the mitochondria, and the small plastics were filled with large plastic nucleotids. This enlargement of the plastic nucleoids occurred before the synthesis of ribulose-1,5-bisphosphate carboxylase/oxygenase and the development of thylakoids.
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