Mitochondrial Mutations Impair Signal Transduction inDictyostelium discoideumSlugs

The necessity of mitochondrial genome DNA for normal development ofDictyosteliumcells

“…Importantly, this developmental phenotype is similar to that of the transformant in which about a half of mitochondrial rps4 gene was disrupted by means of homologous recombination (Inazu et al, 1999). The failure of ρ ∆ slugs to exert normal phototaxis is also consistent with the finding that disruption of the mt-lrRNA in a subpopulation of mitochondria impaires photosensory signal transduction at the slug stage (Wilczynska et al, 1997).…”

“…In Dictyostelium discoideum Ax-2, the rps4 gene encoding for mitochondrial ribosomal protein S4 (RPS4) has been shown to be specifically expressed during the transition (GDT) of Ax-2 cells from growth to differentiation; rps4 HR cells in which an about half of rps4 gene is disrupted by means of homologous recombination exhibit greatly delayed differentiation after starvation, whereas rps4 OE cells overexpressing the rps4 mRNA in the extra-mitochondrial cytoplasm perform enhanced differentiation through car1 induction (Inazu et al, 1999). Disruption of the large subunit rRNA (mt-lrRNA) gene in a subpopulation of mitochondria impairs photosensory and themosensory signal transduction in the migrating slug stage of D. discoideum (Wilczynska et al, 1997). Also, the germ cell line is determined by the mt-lrRNA in Drosophila (Kobayashi and Okada, 1989;Iida and Kobayashi, 1998).…”

“…Impaired phototaxsis of slugs derived from ρ ∆ cells Wilczynska et al (Wilczynska et al, 1997) have reported that in many heteroplasmic mitochondrial gene disruptants of Dictyostelium the phototaxis of migrating slugs as well as vegetative growth of cells are greatly impaired, particularly in mitochondrial large rRNA (mt-lrRNA)-deficient mutants. This raised the possibility that slugs derived from ρ ∆ cells might also exhibit impaired phototaxis.…”

“…the ratio of prestalk/prespore cells in a slug or stalk cells/spores in a sorocarp): application of specific inhibitors of CN-resistant respiration to starved Dictyostelium cells induces the formation of unique cell masses, in which almost all of the cells differentiate into prestalk cells and then stalk cells, thus being completely devoid of prespore and spore differentiation (Matsuyama and Maeda, 1995). The large subunit (mt-lrRNA) of Dictyostelium mitochondrial rRNA is also essential for phototaxis and thermotaxis of the migrating slug (Wilczynska et al, 1997). Taken together, these data offer indications of the dynamic involvements of mitochondria and mitochondrial DNA in a variety of processes during Dictyostelium development.…”

Antisense RNA Inhibition of the β Subunit of theDictyostelium discoideumMitochondrial Processing Peptidase Induces the Expression of Mitochondrial Proteins

“…In addition, depletion in the mtDNA caused deficiencies in cell aggregation 16) and in cell-type differentiation. 17,18) Furthermore, deficiencies in certain nuclear-encoded mitochondrial proteins cause defects in chemotaxis to cAMP 19) and in cell-type differentiation. 20) Despite increasing attention to the role of mitochondria in development, little is known concerning mitochondrial biogenesis in D. discoideum.…”