Proteolysis and orientation in Dictyostelium slugs

Abstract

It has been long known that the migrating slugs of the cellular slime moulds are highly sensitive to their environment and orient towards light and in temperature and chemical gradients. There is considerable evidence from past work that these orientations are governed by NH, which affects the rate of movement of cells within the slug with such precision that orientation to the external stimuli is achieved. In order to test this hypothesis further, various ways to alter the internal NH, concentration were devised. Substances that either increased or decreased proteolysis were applied to one side of the tip of a slug, thereby affecting its orientation. Some of the treatments strongly support the role of internally produced NH, in orientation, and all the treatments produce results that are consistent with the hypothesis.

An expanded phylogeny of social amoebas (Dictyostelia) shows increasing diversity and new morphological patterns

“…This tangling indicates the loss of proximity inhibition, normally the result of NH 4 sensing [21]. The new Group 4 species, D. gargantuum , is the single largest dictyostelid described thus far, with huge (by microbial standards) solitary sorocarps (3-8 mm or more tall if erect and 20-30+ mm or more if prone; Additional file 1) [23]. …”

Temporal and spatial expression of ammonium transporter genes during growth and development of Dictyostelium discoideum

“…Early in the developmental cycle, coalescing amoebae differentiate into pre-spore and pre-stalk cells. Ammonia production and ammonia concentrations are a reflection of the producing cell type (Feit et al, 1990;Cotter et al, 1992;Bonner, 1993) and of the macro-and/or microenvironment of the cell (Sussman and Schindler, 1978). Developing Dictyostelium cells use ammonia signaling for monitoring the environment, morphological changes and differentiation events that have occurred, and as a result, their progression through the developmental program.…”

Identification of novel elements which regulate the cell-type specificity of Dictyostelium 7E gene expression

“…Interestingly, a number of groups have reported the existence of a population of cells that express the cell surface 5′ nucleotidase gene (Bonner et al, 1955; Krivanek and Krivanek, 1958). These cells are dispersed throughout the prespore region of the migratory slug, in a similar manner to the distribution of ALCs, and are largely absent from the prestalk region at the anterior of the tip (Krivanek and Krivanek, 1958).…”