Calcium, cellular adhesion and aggregation competence in the cellular slime mold Polysphondylium violaceum

Glorin-regulated protein synthesis in Polyspondylium violaceum

Protein synthesis by Polyspondylium violaceum in response to the chemoattractant glorin was analyzed by two-dimensional gel electrophoresis to determine if glorin can affect gene expression. When cells developing in a shaking suspension culture were given glorin, five proteins exhibited significantly increased and three proteins exhibited decreased incorporation of L-[35S]methionine. Glorin was active from 10-1000 nM, a concentration range within which cells are chemotactically active. The extent of the response was dependent on the concentration and the length of exposure to glorin. This evidence suggests that glorin may act in part to mediate changes in gene expression during development.

Developmental regulation of production of an aggregation-stimulating factor from the cellular slime mold Polysphondylium violaceum

An excreted, dialyzable component(s) produced during development of wild-type Polysphondylium violaceum has been previously shown to stimulate aggregation of aggregateless mutants in the complementation group aggA. Production of this aggregation-stimulating factor, called D factor, is greater during development in liquid culture than during development on a surface. after partial purification of crude D factor using high performance liquid chromatography, multiple species are found that retain the ability to stimulate aggregation of the aggA mutants. The three major components (DfA, DfB, and DfC) show decreasing polarity based on purification using reverse-phase chromatography. The proportion of each component secreted varies, depending on the developmental conditions (surface versus liquid) and the time after starvation when the factors are isolated. Preliminary physical and chemical characterization of the three D factor components suggests that they are related.

Extracellular cyclic AMP during development of the cellular slime mold Polysphondylium violaceum: comparison of accumulation in the wild type and an aggregation-defective mutant

Cyclic AMP was synthesized by Polysphondylium violaceum after starvation and during the preaggregation stage of development. Most of the newly synthesized cyclic AMP accumulated in the extracellular medium, with very little change in the intracellular cyclic AMP concentration. The addition of 10(-3) to 10(-6) M exogenous cyclic AMP to starved amoebae caused a 20 to 50% decrease in the number of aggregation centers formed compared with untreated controls. An aggregation-defective mutant of P. violaceum (strain aggA586) excreted or accumulated very little cyclic AMP. Strain aggA586 aggregated normally in the presence of a dialyzable, excreted product (D factor) produced by wild-type amoebae. When the mutant was incubated with D factor, cyclic AMP accumulated in the medium, and the amount accumulated depended on the amount of D factor added to the mutant amoebae.