A temperature-dependent block in spore differentiation is transduced intercellularly by Dictyostelium discoideum

Strain HH31 of Dictyostelium discoideum is abnormal in the sense that at 27 degrees C it fails to produce spores and all or nearly all of the cells become stalk cells. In interstrain chimeras produced at the restrictive temperature, this strain shares with strains A3 or M28 the potential to control spore differentiation in neighboring cells. If HH31 is in numerical excess in slugs, then spore formation by A3 or M28 is suppressed by a factor of 20 or more. In contrast, an excess of A3 cells stimulates the formation of spores by HH31; the rescue affects fewer than one in 1000 HH31 cells though this represents a rescue coefficient of up to 2 X 10(3). The transcellular influence mediated by HH31 is rendered locally since it cannot traverse a thin membrane. It is not an artifact of unfavorable positioning of the test cells because in the slug they accumulate in the prespore region. The temperature-dependence of the self-differentiation of HH31 and its effect on A3 or M28 are altered coordinately in a spontaneous variant of HH31. We suggest that HH31 exerts, and is receptive to, a local effect on and by neighboring cells. This may be mediated by plasma membrane wheat germ agglutinin receptors, since their expression is also found to be under coordinate temperature control in HH31 and its variant.