Inhibition of endosomal trafficking by brefeldin A interferes with long‐distance interaction between chloroplasts and plasma membrane transporters

Abstract

The huge internodal cells of the characean green algae are a convenient model to study long-range interactions between organelles via cytoplasmic streaming. It has been shown previously that photometabolites and reactive oxygen species released by illuminated chloroplasts are transmitted to remote shaded regions where they interfere with photosynthetic electron transport and the differential activity of plasma membrane transporters, and recent findings indicated the involvement of organelle trafficking pathways. In the present study, we applied pulse amplitude-modulated microscopy and pH-sensitive electrodes to study the effect of brefeldin A (BFA), an inhibitor of vesicle trafficking, on long-distance interactions in Chara australis internodal cells. These data were compared with BFA-induced changes in organelle number, size and distribution using fluorescent dyes and confocal laser scanning microscopy. We found that BFA completely and immediately inhibited endocytosis in internodal cells and induced the aggregation of organelles into BFA compartments within 30-120 min of treatment. The comparison with the physiological data suggests that the early response, the arrest of endocytosis, is related to the attenuation of differences in surface pH, whereas the longer lasting formation of BFA compartments is probably responsible for the acceleration of the cyclosis-mediated interaction between chloroplasts. These data indicate that intracellular turnover of membrane material might be important for the circulation of electric currents between functionally distinct regions in illuminated characean internodes and that translational movement of metabolites is delayed by transient binding of the transported substances to organelles. 122

Effects of chloroplast–cytoplasm exchange and lateral mass transfer on slow induction of chlorophyll fluorescence in Characeae

“…This rate was 25–30% lower than the speed of individual particle movement as measured with a stopwatch. Consistently lower rates of the fluorescence wave propagation compared to the streaming velocity were observed previously and ascribed to multiple binding–release events between laterally transported metabolites and ectoplasmic vesicles (Bulychev & Foissner, 2020).…”

“…Basic similarity of slow fluorescence induction in the absence and presence of cyclosis (Figure7A) might raise a possibility that Chl fluorescence changes induced by illumination of a remote cell region in untreated cells arise from the internal production of stromal reductants under dim light during the passage of the cytoplasm enriched with photometabolites, i.e., in a period when the concentration gradient across the envelope membranes in the AOI hinders the metabolite efflux. However, this possibility is at variance with observations that the F 0 response to illumination of a remote cell region remains evident for 1-2 min after placing the cell in darkness(Bulychev & Foissner, 2020;Bulychev & Rybina, 2018) when the photosynthetic electron transport is inactive. Thus, the slow stages of fluorescence induction curves in cells of characean algae are sensitive to metabolites carried by cytoplasmic streaming.…”

Brefeldin A inhibits clathrin‐dependent endocytosis and ion transport in Chara internodal cells

“…The formation of BFA bodies and the related decrease in organelle number and membrane surface are probably responsible for the accelerating effect of BFA on long‐distance interaction between chloroplasts [Bulychev et al., 2018; Bulychev and Foissner, 2020].…”

“…Alkaline and acid bands were identified with 4 μM phenol red (phenolsulfonphthalein; Sigma) dissolved in AFW or by tipsensitive antimony pH microelectrodes as described in Bulychev et al (2001). Chlorophyll fluorescence was measured according to Bulychev and Foissner (2020).…”

Insight into the role of clathrin‐mediated endocytosis inhibitors in SARS‐CoV‐2 infection

“…Furthermore, ikarugamycin, isolated from Streptomyces phaeochromogenes, affects CME, 80 whereas brefeldin A, TENin1, and auxin inhibit the formation of clathrin coats pits and ion transport. 81 , 82 , 83 …”