Developmental regulation of the alpha-mannosidase gene in Dictyostelium discoideum: control is at the level of transcription and is affected by cell density.
In Dictyostelium discoideum, there is a group of genes that are expressed following starvation and when exponentially growing cells reach high densities. We have examined the expression of one of these genes, alpha-mannosidase. Using an alpha-mannosidase cDNA probe in Northern (RNA) blot analysis, we have shown that the previously observed increase in alpha-mannosidase enzyme-specific activity during development is due to an increase in the levels of alpha-mannosidase mRNA. mRNA levels reach a maximum by 8 h of development and then begin to decline by 14 to 22 h. Using nuclear run-on analysis, we have found that this gene is regulated at the level of transcription. We also examined the effects of cell-cell contacts, cyclic AMP levels, and protein synthesis on expression of this gene and found that they were not critical in regulating its expression. However, cell density did play a major role in the expression of alpha-mannosidase. High cell density or the presence of buffer conditioned by high-density cells was sufficient to induce expression of alpha-mannosidase, indicating that this is one of the prestarvation response genes. Finally, the alpha-mannosidase gene was not expressed in aggregation-negative mutant strain HMW 404.
Schatzle
J
J
Department of Microbiology and Immunology, LSU Medical Center, Shreveport 71130.
Rathi
A
A
Clarke
M
M
Cardelli
J A
JA
D015152:Blotting, Northern; D015342:DNA Probes; D004023:Dictyostelium / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D007700:Kinetics; D008361:Mannosidases / Q000235:genetics*; D012331:RNA, Fungal / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics / Q000302:isolation & purification; D013997:Time Factors; D014158:Transcription, Genetic; D043323:alpha-Mannosidase
D015342:DNA Probes; D012331:RNA, Fungal; D012333:RNA, Messenger; D008361:Mannosidases; D043323:alpha-Mannosidase