Functional characterization of isolated plastids from two marine diatoms |
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Authors: | Claus Wittpoth Peter G Kroth Katharina Weyrauch Klaus V Kowallik Heinrich Strotmann |
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Institution: | Institut für Biochemie der Pflanzen, Heinrich-Heine-Universit?t Düsseldorf, Universit?tsstr.1, D-40225 Düsseldorf, Germany, DE Botanisches Institut, Heinrich-Heine-Universit?t Düsseldorf, Universit?tsstr.1, D-40225 Düsseldorf, Germany, DE
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Abstract: | A protocol for the isolation of intact plastids from two marine centric diatoms, Odontella sinensis (Greville) Grunow and Coscinodiscus granii Gough, has been worked out. The cells were broken in a Yeda Press, and the intact plastids were purified by centrifugation
in Percoll gradients. Electron microscopy indicates that at least one of the four envelope membranes is present in the isolated
plastids. The plastids are photosynthetically active as proven by CO2 fixation which was measured by light-dependent oxygen evolution. Rates up to 50 μmol O2 · (mg Chl)−1 · h−1, i.e. about 40% of the in vivo rate of photosynthesis were obtained. The inhibition of CO2 fixation by external phosphate and the ability of the plastids to reduce added 3-phosphoglycerate photosynthetically indicate
the presence of a phosphate translocator in the envelope of the diatom plastids. Light-dependent O2 evolution upon addition of nitrite indicates the presence of nitrite reductase in these plastids. Purified envelope membranes
of Odontella plastids analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis contain polypeptides similar to those of the
envelope of higher-plant chloroplasts. However, there are additional bands present, which in part may be constituents of the
two additional envelope membranes (“chloroplast endoplasmic reticulum”) and in part may represent additional components of
the inner membranes.
Received: 1 August 1997 / Accepted: 2 February 1998 |
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Keywords: | : Diatom Envelope membranes Photosynthetic activity Plastid isolation |
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