, Volume 216, Issue 3, pp 227-238

First online:

Architecture of the Golgi apparatus of a scale-forming alga: biogenesis and transport of scales

  • E. K. HawkinsAffiliated withDepartment of Biology, City College of City University of New York
  • , J. J. LeeAffiliated withDepartment of Biology, City College of City University of New York

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Mechanisms of transport of secretory products across the Golgi apparatus (GA) as well as of scale formation in prymnesiophytes have remained controversial. We have used a quantitative morphological approach to study formation and transport of scales across the G A in haploid cells ofPleurochrysis sp. The GA of these cells differs from the GA of higher plants in at least six morphological characteristics. Our results show that scales form in the trans-Golgi network (TGN) and transit the TGN in heretofore unrecognized prosecretory vesicles. Prosecretory vesicles differentiate into secretory vesicles prior to exocytosis of scales to the cell surface. Because prosecretory vesicles are only fragments of TGN cisternae, the classical model of cisternal progression is not a valid mechanism of transport in this alga. TGN transport vesicles are also involved in scale formation; however, the role of tubular connections between cisternae of a single stack-TGN unit is not clear. The relationship of two morphological types of cisternal dilations to a membrane-associated, bottlebrush-shaped macromolecule of novel morphology suggests a new hypothesis for the biogenesis of scales.


Golgi apparatus Pleurochrysis sp. Trans-Golgi network Algal-scale biogenesis Algal-scale transport Quantitative morphology