A MUTANT OF DICTYOSTELIUM-MUCOROIDES LACKING THE SOROPHORE SHEATH ANDPRIMARY MACROCYST WALL

A mutant of Dictyostelium mucoroides was isolated following treatment with nitrosoguanidine. This mutant produced morphologically aberrant s orocarps and macrocysts. The absence of a sorophore sheath and primary macrocyst wall was confirmed by light microscopy, fluorescence micros copy of both calcofluor and fluorescein-conjugated concanavalin A-stai ned specimens, and by scanning electron microscopy. Mutant sorocarps f ormed without a sorophore sheath were normally proportioned, but had w eak, curly, cellular stalks. Macrocysts without the primary wall did n ot cluster as did the wild-type macrocysts and often were irregular in shape rather than spherical. These results suggest a common origin fo r the pseudoplasmodial and sorophore sheath and the primary macrocyst wall in cellular slime molds.