ABSTRACT
SodD, a Cu/Zn superoxide dismutase in Dictyostelium discoideum, shows 48% identity to the cytosolic Cu/Zn superoxide dismutase (SOD) of Saccharomyces cerevisiae (SOD1). The sodD gene is expressed in D. discoideum cells at late-developmental stages. However, gene expression was not detected in the sporeless mutant, indicating that sodD is a spore cell-specific gene. The D. discoideum mutant, in which sodD was disrupted, grew and formed a multicellular structure normally, therefore the gene is not essential for growth and development. The mutant spores were sensitive to UV-light compared to the wild-type spores, indicating that SodD protects spores from cellular damage caused by UV-light.
Subject(s)
Dictyostelium/enzymology , Dictyostelium/genetics , Protozoan Proteins/genetics , Sequence Analysis, DNA , Sequence Homology, Amino Acid , Superoxide Dismutase/genetics , Amino Acid Sequence , Animals , Base Sequence , Dictyostelium/radiation effects , Genes/radiation effects , Molecular Sequence Data , Mutation , Protozoan Proteins/radiation effects , Sequence Analysis, DNA/methods , Superoxide Dismutase/radiation effects , Ultraviolet RaysABSTRACT
Genes for the cell-counting factors in Dictyostelium discoideum, countin and countin2, are considered to control the size of the multicellular structure of this organism. A novel gene, countin3, that is homologous to countin and countin2 genes (49 and 39% identity in amino acid sequence, respectively) was identified in the D. discoideum genome. The expression of countin3 was observed in the vegetatively growing cells, decreased in the aggregating stage, increased in the mid-developmental stage and decreased again in subsequent stages. This expression pattern is different from that of countin and countin2. The distinct expression kinetics of three genes suggests that they would have unique roles in size control of D. discoideum.
Subject(s)
Dictyostelium/chemistry , Dictyostelium/genetics , Protozoan Proteins/chemistry , Protozoan Proteins/genetics , Amino Acid Sequence , Animals , Base Sequence , Molecular Sequence Data , Protozoan Proteins/isolation & purification , Reverse Transcriptase Polymerase Chain Reaction , Sequence Alignment , Sequence Homology, Amino AcidABSTRACT
Genes for Copper/Zinc superoxide dismutases, designated sodA and sodB, in the cellular slime mold Dictyostelium discoideum were analyzed. It was found that these gene products contain charged amino acid residues and hydrophobic stretches in their N-terminal regions, suggesting that they are extracellular Cu/Zn superoxide dismutases. The sodA and sodB are expressed in cells in the growth phase and throughout the developmental phases, suggesting that they are the housekeeping genes. The sodA is induced by H(2)O(2) exposure but not by UV irradiation, whereas sodB is induced both by H(2)O(2) exposure and UV irradiation. Such distinct kinetics of the expression patterns suggests that these enzymes play unique roles in D. discoideum.
