Somatic fusion between cell wall mutants of Chlamydomonas reinhardi

Abstract

SOMATIC FUSION has recently been used to isolate hybrids from auxotrophic mutants of fungi^1,2, yeast³ and mosses^4,5. These fusions were performed by using polyethylene glycol (PEG) and/or CaCl₂ solutions on protoplasts which were prepared from cells of tissues treated with enzyme mixtures to dissolve the cell wall. In the unicellular green alga Chlamydomonas mutant strains unable to make a cell wall have been isolated^6,7. Such mutants, similar to plant protoplasts prepared by enzymatic digestion, can be easily grown in defined liquid or agar media⁸. However, they differ from true protoplasts in that they do not burst in hypotonic medium or even in distilled water, indicating that some mechanism of osmoregulation is present⁶. It was thus of interest to determine whether these cell wall mutants could be used as plant protoplasts in fusion experiments. We report here the isolation of stable fusion products obtained from cell wall haploid mutants of Chlamydomonas reinhardi having the same mating type (mt⁺) and bearing genetic markers of auxotrophy.