Disruption of glycogen phosphorylase gene expression in Dictyostelium: evidence for altered glycogen metabolism and developmental coregulation of the gene products.
Glycogen phosphorylase 1 and 2, the isozymes responsible for glycogen degradation, are encoded by separate genes in Dictyostelium. The two gene products display different transcriptional and translational expression and distinct post-translational regulation. Using DNA-mediated transformation, Dictyostelium clones which lacked either glycogen phosphorylase 1 or 2 (gp1 or gp2) expression were obtained. The loss of either enzyme did not change axenic growth patterns, developmental progression, or gross organismic morphology. In gp1- strains, glycogen accumulated to a 17- to 28-fold higher level during late stationary phase without any obvious detrimental effects. This implies that no alternative pathway for glycogen degradation is present in amoebae, and that glycogen metabolism is not critical for vegetative cell growth. Developmental glycogen concentrations were not altered significantly in any of the transformants, but in gp2- cells the posttranslational regulation of the intact gp1 enzyme was apparently modulated to compensate for the loss of gp2. Western blots of microdissected, lyophilized Dictyostelium slugs and early culminates showed that gp2 was found in both prestalk and prespore cells, with a slight enrichment in prespore cells. The gp1 protein was highly enriched in prestalk cells in the parental strain. In gp2- transformants, however, gp1 was detected in equal amounts in both cell types. The loss of gp2 led to a shift in the cell-type-specific expression pattern of gp1, presumably due to developmental coordinate regulation of gp1 and gp2 at the translational and/or transcriptional level.
Rogers
P V
PV
Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg 24061.
Sucic
J F
JF
Yin
Y
Y
Rutherford
C L
CL
D000818:Animals; D004271:DNA, Fungal / Q000235:genetics; D004023:Dictyostelium / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D006003:Glycogen / Q000378:metabolism*; D006005:Phosphorylases / Q000096:biosynthesis / Q000235:genetics*; D013696:Temperature; D014170:Transformation, Genetic
D004271:DNA, Fungal; D005656:Fungal Proteins; D006003:Glycogen; D006005:Phosphorylases