Fig. 6. Rescue of culmination of P4H1^- slugs by P4H1-expressing cells, and accumulation of P4H1-expressing cells in the slug tip. (A) Various ratios of parental (Ax3) and P4H1a^- cells were mixed at time 0, developed under ambient conditions, and harvested to count detergent-resistant spores after 48 hours. The straight line describes the calculated spore number if only Ax3 formed spores independent of an effect from P4H1a^- cells. The vertical bar indicates that 20% of cells are normally pre-stalk cells. (B) RFP-expressing normal Ax3 cells were mixed with unlabeled cells, as indicated, in a 7:93 ratio at the start of development. Flattened 16 hour slugs were photographed by phase contrast and for RFP-fluorescence. (C) In the reverse experiment, RFP-expressing P4H1^- cells were mixed with unlabeled cells, as indicated, in a 3:7 ratio. Numbers below image represent the average ratio of mean intensity in the pre-stalk region (demarcated by three white dots) to that of the pre-spore (remaining) region, for multiple slugs (n=3-6). (D) Cultures shown in panel B were allowed to culminate, and stalks were examined. Examples in B and D are typical (n>10). (E) Spore numbers were determined in the mixtures shown in D and for Ax3 and P4H1a^- cells alone (left panel). Percent of spores that were red in the mixtures is shown in the right panel. Results are representative of two independent experiments.