Figure 1.

Diagram of screening procedures for the SN mutant cells. The Gβ null cells were transformed with a library of randomly mutagenized gβ cDNA. The mixture of transformants, expressing Gβ alleles of wild type, SN, and nonfunction, was screened using two procedures. (A) The mixture of transformants was plated on a bacterial lawn, and cells expressing SN or nonfunctional Gβ alleles, which form aggregation minus plaques (agg⁻), were isolated. Clones that synergized and formed the chimeric fruiting bodies with wild-type cells were collected as SN candidates, whereas clones that did not form chimeric structures with wild-type cells were discarded. (B) The mixture of transformants was plated on DB agar, and the fruiting bodies containing spores were collected. These comprise cells only carrying SN or wild-type Gβ alleles. Spore cells were then plated on bacterial lawns, and cells from agg⁻ plaques were isolated as SN candidates.