Characterization of Novel Cytokinesis-defective Mutants of Chlamydomonas reinhardtii

抄録

We isolated 2 independent cytokinesis-defective mutants, inc-1 and inc-2, of the unicellular green alga Chlamydomonas reinhardtii through DNA insertional mutagenesis. Characterization of the mutants, using fluorescence microscopy and microfluorometry, revealed that progression of furrowing begins in inc cells after nuclear division. Unlike wild-type cells, however, the cleavage furrow of the dividing cells disappears before cytokinesis. Successive nuclear divisions with incomplete cytokinesis produce multinucleate cells. Additionally, chloroplast autofluorescence revealed that the chloroplast fails to divide throughout the process of cytokinesis in the mutant cells. We also examined the number of chloroplast nucleoids (cp-nucleoids) and chloroplast DNA (cpDNA) content per chloroplast as indicators of cell cycle. We observed cp-nucleoids through DAPI staining and measured the intensity of DAPI fluorescence with a video-intensified microscope photon-counting system (VIMPCS). Both the number of cp-nucleoids and cpDNA content per chloroplast increased under incomplete cytokinesis in inc cells. The inc mutants represent novel cytokinesis-defective mutants of C. reinhardtii.