Biosynthesis and Turnover of Cell Wall Glycoproteins during the Vegetative Cell Cycle of Chlamydomonas reinhardii

Jürgen Voigt Institut für Allgemeine Botanik und Botanischer G arten , Universität Hamburg, Ohnhorststraße 18, D-2000 Ham burg 52, Bundesrepublik Deutschland Z. Naturforsch. 41c, 885-896 (1986); received June 25, 1986 Biosynthesis, Cell Cycle, Cell Wall, Chlamydomonas reinhardii Glycoproteins Biosynthesis and turnover of the different cell wall components have been studied during the vegetative cell cycle of Chlamydomonas reinhardii by pulse-labelling with [3H]proline and [35S]methionine and by pulse-chase experiments. Two phases of biosynthesis of insoluble cell wall material could be distinguished: 1. de novo synthesis of the daughter cell walls during cytokinesis and 2. cell wall enlargement during cell growth. During the cell enlargem ent period, a turnover of the insoluble wall component was observed. The released fragments were found to be accumulated in the culture medium. The LiCl-soluble cell wall glycoproteins were found to be precursors of the insoluble cell wall layer. Biosynthesis of the LiCl-soluble cell wall glycoproteins was observed mainly during the time period between cytokinesis and the end of the following cell enlargem ent period. Labelling of all the cell wall components was found to be strongly reduced during the time period between the end of the growth phase and cytokinesis. During cytokinesis, labelling of the insoluble cell wall material preceded the incorporation of radioactive precursors into the LiCl-soluble wall fraction.