Adenylyl cyclase G, an osmosensor controlling germination of Dictyostelium spores.
Dictyostelium cells express a G-protein-coupled adenylyl cyclase, ACA, during aggregation and an atypical adenylyl cyclase, ACG, in mature spores. The ACG gene was disrupted by homologous recombination. acg- cells developed into normal fruiting bodies with viable spores, but spore germination was no longer inhibited by high osmolarity, a fairly universal constraint for spore and seed germination. ACG activity, measured in aca-/ACG cells, was strongly stimulated by high osmolarity with optimal stimulation occurring at 200 milliosmolar. RdeC mutants, which display unrestrained protein kinase A (PKA) activity and a cell line, which overexpresses PKA under a prespore specific promoter, germinate very poorly, both at high and low osmolarity. These data indicate that ACG is an osmosensor controlling spore germination through activation of protein kinase A.
van Es
S
S
Cell Biology Section, Institute for Molecular Plant Sciences, University of Leiden, Wassenaarseweg 64, 2333AL Leiden, The Netherlands.
Virdy
K J
KJ
Pitt
G S
GS
Meima
M
M
Sands
T W
TW
Devreotes
P N
PN
Cotter
D A
DA
Schaap
P
P
D000262:Adenylyl Cyclases / Q000502:physiology*; D000818:Animals; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D004023:Dictyostelium / Q000201:enzymology* / Q000502:physiology; D005656:Fungal Proteins / Q000502:physiology*; D016254:Mutagenesis, Insertional; D015800:Protozoan Proteins; D015398:Signal Transduction; D013172:Spores, Fungal / Q000502:physiology*; D014882:Water-Electrolyte Balance
D005656:Fungal Proteins; D015800:Protozoan Proteins; D017868:Cyclic AMP-Dependent Protein Kinases; C101765:ACG protein, Dictyostelium discoideum; D000262:Adenylyl Cyclases