Quantitative Evaluation of Stromule Frequency at Hourly Intervals in Arabidopsis Stomatal Guard Cell Chloroplasts

抄録

Stromules are tubular structures that emerge from chloroplasts and other types of plastid. Although stromules have roles in plant immunity, little is known about other physiological functions of stromules or the significance of their formation, extent of protrusion and frequency of occurrence. In this study, we quantified the mean frequency of stromules occurrence in stomatal guard cells every hour during the diurnal cycle in developing and developed cotyledons in Arabidopsis seedlings. Stromule mean frequency was not constant during the diurnal cycle, but gradually increased and decreased, resulting in a local peak every 3–4 h. Observations in continuous light revealed that the variation in stromule mean frequency was independent of the lighting conditions. These results provide novel information about stromule formation, showing synchronized and periodic patterns of stromule frequency throughout the day-night cycle in guard cells of developing cotyledons.