78. Spiegel, F. W., Olive, L. S., and R.
M. Brown, Jr. 1979. Roles of action during sporocarp culmination
in the simple mycetozoan Planoprotostelium aurantium. Proc.
Nat. Acad. Sci. U.S.A. 76(5):2335-2339.
78. Abstract
Developing unicellular fruiting bodies of
the protostelid Planoprotostelium aurantium examined by
electron microscopy are shown to have a cortical zone of microfilaments
that surrounds the lower portion of the sporogenic cell and ex-tends
into a cytoplasmic plug that fills the lumen of the tubular, microfibrillar
stalk. Labeling with the S-l fragment of myosin indicates that
the microfilaments are actin. A model is proposed in which the
actin is involved both in a contractile process that serves to
raise the sporogen off the substrate at the tip of the stalk and
in a cytoskeletal role by either directly or indirectly localizing
the synthesis and orientation of the stalk tube microfibrils.
The process of culmination in protostelids is compared to that
of the multicellular dictyostelid cellular slime molds.