A Simple Mechanism for Complex Social Behavior
Figure 6
lsrA− exhibits differences in both clonal and chimeric spore allocation.
(A) Spore:stalk ratios. Cells from dissociated slugs were stained with a prespore cell–specific antibody and the percentage of stained cells measured. The spore:stalk ratio of wild type is 80:20±1.5, whereas the spore:stalk ratio of lsrA− is 60:40±2.3 (t test, t16 = 22.714, p<0.001). (B) Total spore production (measured as the relative output number of spores compared to the input number of amoebae) after fruiting body formation in lsrA− is reduced compared to wild type cells during clonal development (t test, t22 = 9.682, p<0.001). (C) Expression of the prestalk-specific gene, ecmA, was measured by quantitative PCR in wild type and lsrA− mutant cells during development. Expression is higher in lsrA− cells compared to wild type. Results are averages and standard deviations of three biological replicates, where each replicate was performed in triplicate. (D) Quantification of the contribution of lsrA− cells to chimeric fruiting bodies when mixed at different input frequencies. Dotted line shows a fair interaction in which both genotypes contribute equal numbers to spores. Red line (calculated using the fixed allocation model [1]) shows contribution of lsrA− cells to spores predicted by fixed allocation. Blue squares show the observed contribution of lsrA− cells to the sporehead, with best fit regression line (blue line, least-squares differences, F1,4 = 409.8, p<0.001), demonstrating a shift in behavior in chimera that deviated from that expected based on clonal allocation.