FIG. 7.

Molecular events during the M. xanthus developmental program (top) in relation to aggregation and sporulation (bottom). The roles of the developmental gene and protein expression patterns that are assayed in the espA mutants are depicted; see text for details. Pkn14 phosphorylates MrpC (data not shown), which prevents MrpC2 accumulation (35). EspA may repress protein accumulation of MrpC. Solid lines represent direct interactions; dashed lines indicate that mechanisms of action are indirect or unknown. The long horizontal arrow represents time. Groups of M. xanthus cells (gray rectangles) first responding to nutrient limitation and A-signal (i), begin to aggregate (ii) into mounds (iii) and then form spores (gray circles) within the mounds (iv).