Thermotaxis of Dictyostelium discoideum amoebae and its possible role in pseudoplasmodial thermotaxis

Abstract

Thermotaxis by individual amoebae of Dictyostelium discoideum on a temperature gradient is described. These amoebae show positive thermotaxis at temperatures between 14°C and 28WC shortly (3 hr) after food depletion. Increasing time on the gradient reduces the positive thermotactic response at the lower temperature gradients (midpoint temperatures of 14, 16, and 18°C), and amoebae show an apparent negative thermotactic response after 12 hr on the gradient. The thermotaxis response curve for "wild-type" amoebae after 16 hr on the gradient is similar to that shown for the pseudoplasmodia. Growth of the amoebae at a different temperature causes a shift in the thermotaxis response curve for the amoebae. This adaptation is similar to that shown for the pseudoplasmodia. Two mutants in thermotaxis, H0428 and H0813, show changes in amoebal thermotaxis similar to the observed changes in pseudoplasmodial thermotaxis. On the basis of the similarities between these responses, thermotaxis by the amoebae is proposed to be the basis for thermotaxis by the multicellular pseudoplasmodium.Amoebae of the cellular slime mold Dictyostelium discoideum live and grow in the mulch on the forest floor, where they feed on bacteria. Upon depletion of the food supply, the amoebae aggregate, forming a multicellular pseudoplasmodium that eventually develops into a sorocarp consisting of a stalk bearing a sorus containing spores. Under the proper conditions, the spores may germinate, releasing amoebae, thus repeating the developmental cycle (1). Much of the work with this organism has been centered upon its development and the fact that one can easily separate growth and cell division from development.Dictyostelium is also being increasingly recognized as an ideal system for the study of sensory transduction in a eukaryotic organism. Sensory responses thus far described are chemotaxis by the amoebae to cyclic AMP (2) and folate (3), both positive and negative phototaxis by the amoebae (4-6), chemotaxis by the pseudoplasmodia to an endogenous "slug turning factor" (7), phototaxis by the pseudoplasmodia (8-11), and positive and negative thermotaxis by the pseudoplasmodia (8, 12, 13). In addition to the phenomenology, work is also progressing toward an understanding both of the primary steps and of the transduction sequence for each of these responses. Moreover, the use of mutants is permitting a study of the interconnections between these various sensory responses.Because of the ease with which the single-celled and multicelled stages may be separated in Dictyostelium, one would also expect this to be an excellent system for studying the expression of a particular sensory transduction system in the two motile forms, the amoebae and the pseudoplasmodia. However, neither chemotaxis nor phototaxis appears to use the same system in the pseudoplasmodia that is used in the amoebae. For example, the amoebae respond to cyclic AMP and folate, whereas the multicellular pseudoplasmodia do not, and the action spectra for phototaxis by the amoebae s...

Quantitative analysis of cell motility and chemotaxis in Dictyostelium discoideum by using an image processing system and a novel chemotaxis chamber providing stationary chemical gradients.

“…Such a model could explain the morphological polarity of amebae, oscillations, persistence, turning behavior not only in chemotaxis but also in thermotaxis and multidirectional pho-Fisher ¢t al. Cell Motility and Chemotaxis in Dictyostelium totaxis, and sign reversals during phototaxis and thermotaxis (Fisher et al, 1984(Fisher et al, , 1985Hong et al, 1981Hong et al, , 1983H/ider and Poff, 1979a,b).…”

Rheotaxis In Uronychia Setigera (Ciliata, Hypotrichida)

“…Furthermore, the efficiency of orientation was calculated according to the formula suggested by Hong, Fontana, and Poff (1983): A% = (nonentnnot or,ent)/ntot X 100, where nonent indicates the number of cells moving upstream ( Fig. 2 D: O , , O?…”

Supercritical self-interference fluorescence microscopy for full-field membrane imaging

“…[11][12][13][14] Distyostelium discoideum locomotion behaviour is often analyzed through chemotaxis and thermoxis studies. 15,16 In dictyostelium, as in vertebrate cells, locomotion is determined by the spatio-temporal pattern of activities of the cytoskeleton and by the strength and dynamics of cell adhesion to a substratum. Global information can be obtained by reducing cell motion to motion of the centroid of two-dimensional cell projections.…”