NEW LOCI IN DICTYOSTELIUM DISCOIDEUM DETERMINING PIGMENT FORMATION AND GROWTH ON BACILLUS SUBTILIS

James H. Morrissey ¹, Steven Wheeler ¹, and William F. Loomis ¹

¹ Department of Biology, B-022, University of California, San Diego, La Jolla, California 92093

Seventeen independently isolated pigmentless (white) mutations in Dictyostelium discoideum are all recessive and fall into three complementation groups identifying two new whi loci in addition to the previously characterized whiA locus. whiB and whiC map to linkage groups III and IV, respectively. In addition, it was discovered that our laboratory stock of NC4, the wild-type strain from which these mutants were derived, has spontaneously lost the ability to grow on Bacillus subtilis. This new mutation, bsgB500, maps to linkage group VII and is not allelic to bsgA. bsgB500 is the first spontaneously derived mutation in D. discoideum that can be used to select heterozygous diploids, and for the first time allows genetic analysis to be routinely performed on strains derived from an unmutagenized background.