Fluorescence microscopy of plastid nucleoids and a survey of nuclease C in higher plants with respect to mode of plastid inheritance

Summary Plastid nucleoids (pt nucleoids) were observed during pollen formation, or in generative cells of mature pollen grains using fluorescence microscopy after staining with 4,6-diamidino-2-phenylindole (DAPI). Nuclease C activity was surveyed using SDS-PAGE and agarose gel nuclease assay methods. InMirabilis jalapa, pt nucleoids were observed both in pollen mother cells and the monocellular pollen grains after meiosis, followed by the complete disappearance both in the generative and vegetative cells at the bicellular pollen grain stage. This observation is a direct evidence of maternal plastid inheritance. By contrast, in the generative cells of mature pollen grains fromRhododendron kaempferi, Zygocactus truncatus, Oenothera laciniata, andO. speciosa, pt nucleoids were clearly observed. Thus cytological evidence convinces the mode of biparental plastid inheritance. Nuclease C activity was clearly detected both in the stamen and pistil ofM. jalapa. InR. kaempferi low nuclease C activity was detected in both organs, but the activity in the stamen was much less than in the pistil. InZ. truncatus, O. laciniata, andO. speciosa, the activities were difficult to detect in both organs. These results suggest a significant role of nuclease C for the digestion of pt nucleoids in the generative cells.Abbreviations EGTA ethylene-glycol-bis-(2-aminoethyl ether)-N, N, N, N-tetraacetic acid - DAPI 4,6-diamidino-2-phenylindole - Nuclease C Ca²⁺ dependent nuclease - SDS-PAGE SDS-polyacrylamide gel electrophoresis - pt nucleoids plastid nucleoids