Zygote and vegetative cell wall proteins in Chlamydomonas reinhardtii share a common epitope, (SerPro)_X

Polyclonal antibodies directed against a (SerPro)₁₀ oligopeptide and a ß-galactosidase/zygote-wall-gene fusion protein were used in in vitro translation/immunoprecipitation experiments to show that (SerPro)_x is a common motif in proteins which assemble into either the zygotic or the vegetative/gametic cell walls of Chlamydomonas reinhardtii. There are at least five, and possibly as many as ten different zygote-specific proteins displaying (SerPro)_x-like epitopes. Zygote-specific cDNAs corresponding to two of these proteins have been previously characterized and shown to encode several regions of (SerPro) ranging from 2 to 9 repeats. In addition, the (SerPro)₁₀ antibody recognizes five vegetative/gamete-specific proteins from cells induced for wall synthesis. One of these five corresponds to the vegetative/gamete-wall glycoprotein GP2, as confirmed by immunoprecipitation with a polyclonal antibody to purified GP2. The GP2 antibody detects epitopes other than (SerPro)_x and also immunoprecipitates a novel zygote-specific protein.