Morphogenetically synchronized Dictyostelium discoideum amoeba were sampled at intervals during development to determine the fates of major cell constituents. Dry weight, total protein and fractions thereof, RNA, free and bound hexoses were followed. None of these except the last appeared to reflect the specific morphogenetic events. Two polysaccharide fractions were encountered which did reflect these events and their syntheses were repressed or disturbed in morphogenetically deficient mutants.
[Show abstract][Hide abstract] ABSTRACT: Free-living amoebae of the cellular slime mouldDictyostelium discoideum aggregate when starved and give rise to a long and thin multicellular structure, the slug. The slug resembles a metazoan
embryo, and as with other embryos it is possible to specify a fate map. In the case ofDictyostelium discoideum the map is especially simple: cells in the anterior fifth of the slug die and form a stalk while the majority of those in
the posterior differentiate into spores. The genesis of this anterior-posterior distinction is the subject of our review.
In particular, we ask: what are the relative roles of individual pre-aggregative predispositions and post-aggregative position
in determining cell fate? We review the literature on the subject and conclude that both factors are important. Variations
in nutritional status, or in cell cycle phase at starvation, can bias the probability that an amoeba differentiates into a
stalk cell or a spore. On the other hand, isolates, or slug fragments, consisting of only prestalk cells or only prespore
cells can regulate so as to result in a normal range of both cell types. We identify three levels of control, each being responsible
for guiding patterning in normal development: (i) ‘coin tossing’, whereby a cell autonomously exhibits a preference for developing
along either the stalk or the spore pathway with relative probabilities that can be influenced by the environment; (ii) ‘chemical
kinetics’, whereby prestalk and prespore cells originate from undifferentiated amoebae on a probabilistic basis but, having
originated, interact (e.g. via positive and negative feedbacks), and the interaction influences the possibility of conversion of one cell type into
the other; and (iii) ‘positional information’, in which the spatial distribution of morphogens in the slug influences the
pathway of differentiation. In the case of possibilities (i) and (ii), sorting out of like cell types leads to the final spatial
pattern. In the case of possibility (iii), the pattern arisesin situ
Journal of Biosciences 12/1992; 17(4):353-394. DOI:10.1007/BF02720094 · 2.06 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.