PRODUCTION OF CELL-WALL POLYPEPTIDES BY DIFFERENT CELL-WALL MUTANTS OF THE UNICELLULAR GREEN-ALGA CHLAMYDOMONAS-REINHARDTII

Three classes of cell wall-defective mutants of the unicellular green alga Chlamydomonas reinhardtii have been described in the literature d iffering with respect to the amounts of cell wall material and its att achment to the plasma membrane, respectively. We have compared the pro duction of the chaotrope-soluble cell wall polypeptides by the differe nt mutants. These experiments have been performed by comparative Weste rn-blot analyses using antibodies raised (1) against the deglycosylati on products of the insoluble wall fraction of wild-type cells, (2) aga inst the deglycosylation product of the '150 kDa' chaotrope-soluble ce ll wall polypeptide and (3) against the carbohydrate side chains of th e Chlamydomonas cell wall glycoproteins, respectively. Considerably di fferent levels of cell wall polypeptides were found in the LiCl-extrac ts from intact cells of the various mutant strains containing the apop lastic, chaotrope-soluble cell wall glycoproteins. No correlation was found between the amounts and the patterns of cell wall glycoproteins present in the LiCl-extracts and the electron microscopical classifica tion of the mutant strains. All the mutant strains were shown to conta in the same amounts and patterns of intracellular cell wall precursors as wild-type cells as revealed by Western-blot analyses of urea-SDS l ysates of LiCl-pretreated cells. These findings indicate that the diff erent mutant strains produce the same set of cell wall polypeptides at the same relative amounts as wild-type cells. However, in the case of some strains belonging to different classes of cell wall mutants and showing differential seggregation patterns in crosses, alterations wer e observed for the pattern of extracellular cell wall polypeptides pre sent in the LiCl-extracts from intact cells and in the culture medium, respectively.