The influence of pH on the choice between sexual and asexual development in Dictyostelium mucoroides

Abstract

The cellular slime mould Dictyostelium mucoroides exhibits clear dimorphism in development which, depending upon environmental conditions, leads to (1) macrocyst formation, a sexual process or (2) sorocarp formation, an asexual process. The present work was undertaken to determine the role of protons in the determination of the developmental mode. Intracellular pH (pHi) was measured at the single-cell level microfluorometrically by use of the pH-sensitive fluorescent dye carboxfluorescein. The proton-pump inhibitor diethylstilboestrol, the protonophore 2,4-dinitrophenol and a weak acid, propionate, were found to convert the developmental mode from macrocyst to sorocarp formation under conditions otherwise favouring macrocyst formation. All of these drugs lowered pHi. Although no significant difference in pHi was detected between dissociated cells shaken in buffers of pH 5.0 and pH 7.0, a marked difference in pHi arose between the two if 5 mM-NH,Cl was included to simulate the expected microenvironment in the cell mass during development. Comparison of the pHi of cells developing toward sorocarps with that of cells developing toward macrocysts revealed a few cells with extremely high pHi ( > 7.30) in the latter population. The results obtained suggested that pHi, or something related to pHi, influences the development a1 choice.

Differential increase in cytoplasmic pH at bud and germ tube formation in Candida albicans: studies of a nongerminative variant

“…The role of cytoplasmic pH (pHi) in the mitogenic signal pathway and control of cell proliferation in several cell types (Grienstein et al 1989) is well known. The role of pH, in dictating cell shape (Tao et al 1987) and morphological transition (Cassone et al 1983;Kaur et al 1988b;Stewart et al 1988Stewart et al , 1989Furukawa et al 1990;Iijima and Maeda 1990) has also been documented.…”