Golgi - An alternative to vesicle transport

Scale synthesis in algae supports the Cisternal Maturation Model for Golgi dynamics. This was the original model for Golgi transport.

Chrysochromulina is a small prymnesiophyte alga. The body is covered with several layers of scales. These scales are made within the Golgi apparatus that is located near the bases of the flagella. This study by the pioneer electron microscopist Irene Manton (1968) J. Cell Sci. 2, 265-72 provided some of the first evidence suppporting the cisternal maturation model of Golgi Dynamics

 

This transmission electron micrograph shows the Golgi and the chloroplasts as well as the scales on the surface of the cell(at the left) in section. The inset figure at the lower right shows two isolated scales (metal shadowed whole mount). Click on the figure for a guided tour.

 

This electron micrograph shows a section of the Golgi in a Chrysochromulina cell with scales at different stages of maturation. 1 is the oldest, and is in a vesicle that is in the process of detaching from the Golgi stack. Scales 2 through 5 are younger with scale 5 being incompletely formed and just barely detectable. Notice that the most immature scale is in the cis-most cisterna, and that the most mature is in the trans-most cisterna. Click on figure for guided tour.

Here is an example of some more elaborate scales from another alga, Pyramimonas. The upper part of the figure (A) shows a section purpendicular to the cell surface. The large scales are on top of a layer of very small scales. The lower part of the figure (B) shows a section through some of the larger scales that is parallel to the cell surface.

These figures show sections through the Golgi apparatus in the prasinophyte alga Pyramimonas. The more mature scales are in the trans-most cisternae and cisternae that are cis to these contain partially assembled scale material. Click on the figure for a guided tour. From Moestrup & Walne (1979) J. Cell Sci. 36, 437-59.