CONFIGURATION PATTERN OF CT-NUCLEOIDS IN DIATOMS

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Configurations of chloroplast-nucleoids (ct-nucleoid) were examined with DAPI-stained diatoms (16 genera, 50 species). The configuration was ring-type in all species except for several Pinnularia and Nitzschia species, in which scattered DAPI-fluorescent globules and short strings of DAPI-fluorescence were observed respectively. As DAPI-fluorescent globules in Pinnularia disappeared by DNase treatment, they were confirmed to contain DNA.These globules were confirmed to be located in the chloroplast by confocal laser microscopy and observations of the sections of the cells embedded in Technovit 7100. These globules corresponded to the discrete areas of thylakoids stack in TEM observation. No membranous structure was detected in these areas. The chloroplasts were isolated and then these globules also isolated. The size of globules were similar to that of each beads in ring-type nucleoid. Employing proteinase K treatment, these globules were lysed and then DNA was diffused. These observat … More ions and experiments prove that the globules scattered throughout the chloroplast are the nucleoids to be a complex of DNA and protein. In Pinnularia, 11 species have the ring-type ct-nucleoid and 9 species have the scattered-type nucleoid as well as the ring-type and 1 species has only the scattered-type. Species with the scattered-type are limited in diatoms of P.sect. Pinnularia and P.sect. Divergentissima. In Nitzschia sigmoidea, we observed that small rectangular pyrenoids were scattered throughout the chloroplasts by propion-carmine staining method. In TEM section, they were lens shape, which was typical in diatoms. Specific localization of Rubisco was detected in this structure using indirect immuno-fluorescence microscopy and electron microscopy with immuno-gold. Although the ring-type nucleoid was not observed in this species, linear DAPI-fluorescence was observed along both sides of the pyrenoids and they seem to be the ct-nucleoids. The configurations of ct-nucleoids in diatoms are diversified as in diatom frustules, and seem to reflect their systematics. Less