Both brefeldin A and latrunculin B treatment induces cytoplasmic aggregation of plasma membrane-associated proteins in epidermal cells, but not in columella cells

Root columella and epidermal cells are crucial for sensing external stimuli, yet the differences in their plasma membrane-associated proteins' vesicular transport systems remain poorly understood. In this study, we explored the responses of these cells to pharmacological treatments using brefeldin A (BFA) and latrunculin B (Lat B). Our study revealed that BFA treatment induces the formation of BFA bodies containing PIN2-GFP and GFP-LTi6a in epidermal cells, with the earliest and most pronounced accumulation occurring in the transition zone, though it is also observable in the meristematic zone. In contrast, such accumulation are virtually undetectable for PIN3-GFP and GFP-LTi6a in columella cells. Similar effects were observed when BFA was replaced with Lat B, suggesting that the absence of these proteins' accumulation may be more closely connected to distinct intracellular vesicular transport mechanisms inherent to columella cells, rather than unconventional secretion pathways. Further analysis shows that Lat B treatment led to significant aggregation of key endomembrane organelles in epidermal cells, including the Golgi apparatus, trans-Golgi network (TGN), recycling endosomes (RE), early endosomes (EE), and late endosomes (LE). In contrast, columella cells displayed slight aggregation, limited to the Golgi apparatus, TGN, and RE, without obvious aggregation of EE or LE. These findings suggest the possibility of cell type specificity in actin filament-mediated intracellular vesicular transport of plasma membrane-associated proteins between columella and epidermal cells.