A prespore gene, Dd31, expressed during culmination of Dictyostelium discoideum

Activation of the prespore and spore cell pathway of Dictyostelium differentiation by cAMP-dependent protein kinase and evidence for its upstream regulation by ammonia.

“…The defect in maturation affects spore cell-specific gene expression and is cell autonomous The Dd3J gene encodes a protein involved in spore integrity that accumulates in prespore cells as they differentiate into spore cells during culmination (Richardson et al, 1991;Richardson and Loomis, 1992). As might be expected from their failure to form morphologically identifiable spores, the Dd3J mRNA does not accumulate to any detectable level in psA -Rm cells ( Figure 3A).…”

“…When wild type cells are incubated in submerged culture, as isolated cells, they do not undergo normal morphogenesis but when they are incubated in the presence of 8-bromo cAMP they express the Dd3J gene and mature into spores (Kay, 1989;Richardson et al, 1991). There is convincing evidence that 8-bromo cAMP acts by entering the cell, rather than through an effect on cell surface cAMP receptors (Kay, 1989).…”

“…They were hybridized with radioactively labelled probes from 1G7 (a cDNA clone derived from a constitutively expressed Dictyostelium mRNA, K.A.Jermyn personal communication), psA and Dp87 (Ozaki et al, 1988, a kind gift of Masao Tasaka). The riboprobe for Dd3J mRNA was prepared from the clone pLGL6 (Richardson et al, 1991) and that for SP60 was prepared from the clone 60.3 (Fosnaugh and Loomis, 1989 …”

A multidrug resistance transporter/serine protease gene is required for prestalk specialization in Dictyostelium.

“…As the stalk tube elongates down through the prespore cell mass, a wave of spiA::lacZ expression propagates from the top of the sorus down (Richardson et al 1994). Expression of spiA can also be induced by addition of 8-Br-cAMP to cells dissociated at the culmination stage and shaken in buffer (Richardson et al 1991). It was therefore proposed that prestalk cells signal the initiation of sporulation, probably by activating the cAMP-dependent protein kinase A (PKA).…”

Disruption of the sporulation-specific gene spiA in Dictyostelium discoideum leads to spore instability.

“…Expression of the spiA gene (known previously as Dd31) correlates with sporulation during development (Richardson et al 1991). Accumulation of the spiA mRNA is observed in prespore cells and spores during culmination but not in amoebas or prestalk or stalk cells.…”