Physiological role of the pyrenoids in the green alga Bryopsis maxima.

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Physiological role of pyrenoids in the marine alga, Bryopsis maxima was studies using several methods as follows.I. Immunocytochemical researches. (1) The localization of ribulose 1,5-bisphosphate carboxylase/oxygenase(RuBisCO) in chloroplasts was examined by immunological techniques. Three strains of monoclonal antibodies against the large subunit of RuBisCO were made for the study. Immunofluorescence and immunoenzymatic studies showed that the large subunit of RuBisCO was concentrated in pyrenoids and on the surface of starch grains surrounding the pyrenoids.(2) The concentration of RuBisCO in Pyrenoids decreased when the alga was kept in the dark or matured to eject the gametes.II Biochemical studies (1) Intact pyrenoid core matrix was isolated by diethyl ether treatment and sucrose density gradient centrifugation using 1.8 M phosphate buffer. The purified pyrenoids contained RuBisCO and more than 10 minor polypeptides. They also showed RuBisCO activity when solubilized(specific activity was 0.62 umol CO2 fixed per mg protein per min). (2) The pyrenoids showed NADH-nitrate reductase activity and contained nitrite. The specific activity was 0.024 umols NO2 formed per mg protein per min, which was 80 times greater than that in the crude chloroplasts extract.III. Molecular biological research The gene of the large subunit of RuBisCO was cloned and sequenced. The gene has a large (2.3 kbp) intron and the product was not subjected to the posttranslational processing.