CDKA and CDKB kinases from Chlamydomonas reinhardtii are able to complement cdc28 temperature-sensitive mutants of Saccharomyces cerevisiae

Cyclin-dependent kinases (CDK) play a key role in coordinating cell division in all eukaryotes. We investigated the capability of cyclin-dependent kinases CDKA and CDKB from the green alga Chlamydomonas reinhardtii to complement a Saccharomyces cerevisiae cdc28 temperature-sensitive mutant. The full-length coding regions of algal CDKA and CDKB cDNA were amplified by RT-PCR and cloned into the yeast expression vector pYES-DEST52, yielding pYD52-CDKA and pYD52-CDKB. The S. cerevisiae cdc28-1N strain transformed with these constructs exhibited growth at 36 °C in inducing (galactose) medium, but not in repressing (glucose) medium. Microscopic observation showed that the complemented cells had the irregular cylindrical shape typical for G₂ phase-arrested cells when grown on glucose at 36 °C, but appeared as normal budded cells when grown on galactose at 36 °C. Sequence analysis and complementation tests proved that both CDKA and CDKB are functional CDC28/cdc2 homologs in C. reinhardtii. The complementation of the mitotic phenotype of the S. cerevisiae cdc28-1N mutant suggests a mitotic role for both of the kinases.