Fluorescence microscopy on dynamic changes of frx B distribution inChlamydomonas reinhardtii

Summary Immunocytology method showed that frx B was primarily located in vesicles adjacent to the pyrenoid inChlamydomonas reinhardtii. In synchronous cells, frx B concentration in these vesicles increased in the light period and decreased in the dark period. Prolonged treatment with 5-fluorodeoxyuridine or aging reduced the detectable cellular frx B content. In these cells, frx B appeared as a single dot attached to the pyrenoid. The frx B content in each mating gamete was initially high. As the mating progressed, frx B-containing vesicles in the male gamete disintegrated while that in the female gamete persisted. The time course of this change coincided with that of the chloroplast DNA nucleoids. Persistant small patches of frx B around the pyrenoid were detected in mature zygotes. Fluorescent membrane potential probe showed that membrane vesicles around the pyrenoid had higher transmembrane potential than other chloroplast membranes. This high membrane potential was sensitive to inhibitors of chlororespiration.