ISOLATION AND CHARACTERIZATION OF CHEMOTAXIS MUTANTS OF CHLAMYDOMONAS-REINHARDTII

Zoospores of Chlamydomonas reinhardtii exhibit chemotaxis towards malt ose, sucrose, xylose, mannitol, and ammonium. Ten independent mutants defective in chemotaxis towards sugars have been isolated. These mutan ts form five phenotypic classes. Genetic analysis of two mutant strain s defective in chemotaxis to maltose (CHE1, CHE3) and two mutant strai ns defective in chemotaxis to sucrose (CHE2, CHE4) indicated that the defect in them depended on single nuclear recessive mutant alleles. Mu tations mal1, mal2, suc1, and suc2 represent four chemotactic loci tha t are unlinked to the marker mt located on the linkage group VI. Four loci are unlinked to each other. These observations suggest that the m al and the suc loci do not constitute a spatially single functional gr oup.