Loss of cargo fluorescence from the Golgi is due to exit of post-Golgi TCs
A. Subjectively, fluorescence of cargo in Golgi elements becomes progressively fainter from 27 to 42 minutes after initiation of transport by shift to 32°C (right-hand panels), but fluorescence of the Golgi resident T2-CFP remains the same (left-hand panels). Figure 2A corresponds to frames from the movies in Additional Fileset 2. Bar: 10 μm.
B. Quantitation of normalized, background subtracted fluorescence signals over time shows that the total level of VSVG3-YFP in the cell remains almost constant, but the level in the Golgi (region indicated by the dotted line in the top left panel) drops linearly to below 60% of the initial level. The inset shows the theoretical rise and fall of cargo levels in the Golgi over a complete period of transport  indicating that cargo is lost in a linear manner from the Golgi for a significant period. VSVG3-YFP in Golgi elements is concentrated compared to VSVG3-YFP in the plasma membrane and so appears brighter in Golgi elements.