Fig. 1. Identification of a novel DIF resistant mutant. (A) Schematic of the selection strategy used to identify the dimC^- mutant. REMI mutagenized cells were subjected to the cAMP-removal stalk-cell induction assay before HL5 growth medium was added. Surviving cells were grown up and subjected to a further two rounds of selection before cloning out. (B) dimC^- cells fail to make stalk cells in the cAMP removal assay. At least three independent assays were performed with comparable results. Data are shown from a representative experiment in which plates were scored in triplicate. Representative pictures are shown on the right. Black arrows highlight vacuolized stalk cells. (C) dimC^- cells make equivalent numbers of spore cells as wild type in the 8-Br-cAMP assay in the absence of DIF. In the presence of DIF, spore cell formation is repressed in both wild-type and mutant cells. At least three independent assays were performed with comparable results. Data are shown from a representative experiment in which plates were scored in triplicate. White arrows highlight representative spore cells. The pictures on the right show that the mutant cells, in contrast to wild type, still do not make stalk cells when treated with DIF. Black arrows highlight vacuolized stalk cells.