A new assay system to classify non-mating mutants and to distinguish between vegetative cell and gamete in Chlamydomonas reinhardtii

Summary A new system is described for the classification of various types of non-mating mutants of Chlamydomonas reinhardtii. This system makes use of two simple assays: one for cell body-agglutinin (Saito et al. 1985), and another for the cell wall lytic enzyme (Matsuda et al. 1987). Both assays use the soluble fraction of homogenates from nitrogen-starved cells. Many non-mating mutants previously isolated were analysed and divided into four main phenotypic classes. This assay method is also a valuable tool for distinguishing between vegetative cells and gametes. Without this assay, verifying gametogenesis is especially difficult in agglutinin-and flagella-deficient cells. We found that wild-type cells, which had been grown for 7 days on TAP plates and lacked flagella, contain neither cell body-agglutinin activity nor lytic enzyme activity in the soluble fraction of their cell homogenates, indicating that these cells can be classified as vegetative. When suspended in nitrogen-free liquid medium, the two activities developed rapidly in parallel to the acquisition of mating ability: a maximum level was reached within two hours.