Int. J. Dev. Biol. 45: 405 - 414 (2001)

Vol 45, Issue 2

Cell cycle phase, cellular Ca2+ and development in Dictyostelium discoideum

Published: 1 April 2001

M Azhar, P K Kennady, G Pande, M Espiritu, W Holloman, D Brazill, R H Gomer and V Nanjundiah

Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, India.

Abstract

In Dictyostelium discoideum, the initial differentiation of cells is regulated by the phase of the cell cycle at starvation. Cells in S and early G2 (or with a low DNA content) have relatively high levels of cellular Ca2+ and display a prestalk tendency after starvation, whereas cells in mid to late G2 (or with a high DNA content) have relatively low levels of Ca2+ and display a prespore tendency. We found that there is a correlation between cytosolic Ca2+ and cell cycle phase, with high Ca2+ levels being restricted to cells in the S and early G2 phases. As expected on the basis of this correlation, cell cycle inhibitors influence the proportions of amoebae containing high or low Ca2+. However, it has been reported that in the rtoA mutant, which upon differentiation gives rise to many more stalk cells than spores (compared to the wild type), initial cell-type choice is independent of cell cycle phase at starvation. In contrast to the wild type, a disproportionately large fraction of rtoA amoebae fall into the high Ca2+ class, possibly due to an altered ability of this mutant to transport Ca2+.