Dictyostelium RasD is required for normal phototaxis, but not differentiation
- Andrew Wilkins1,5,
- Meenal Khosla2,5,
- Derek J. Fraser3,5,
- George B. Spiegelman2,
- Paul R. Fisher3,
- Gerald Weeks2, and
- Robert H. Insall4,6
- 1MRC Laboratory for Molecular Cell Biology and Departments of Physiology, University College London, London WC1E 6BT, UK; 2Department of Microbiology and Immunology and Department of Medical Genetics, University of British Columbia, Vancouver V6T 1Z3, Canada; 3Department of Microbiology, La Trobe University, Bundoora, Victoria 3083, Australia; 4School of Biosciences, Birmingham University, Edgbaston, Birmingham B15 2TT, UK
Abstract
RasD, a Dictyostelium homolog of mammalian Ras, is maximally expressed during the multicellular stage of development. Normal Dictyostelium aggregates are phototactic and thermotactic, moving towards sources of light and heat with great sensitivity. We show that disruption of the gene for rasDcauses a near-total loss of phototaxis and thermotaxis in mutant aggregates, without obvious effects on undirected movement. Previous experiments had suggested important roles for RasD in development and cell-type determination. Surprisingly, rasD − cells show no obvious changes in these processes. These cells represent a novel class of phototaxis mutant, and indicate a role for a Ras pathway in the connections between stimuli and coordinated cell movement.
