A localized differentiation-inducing-factor sink in the front of the Dictyostelium slug

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 90; no. 2; pp. 487 - 491
• Main Authors: Kay, Robert R., Large, Sara, Traynor, David, Nayler, Oliver
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 15-01-1993; National Acad Sciences; National Academy of Sciences
• Subjects: actividad enzimatica; activite enzymatique; Animals; Biochemistry. Physiology. Immunology. Molecular biology; Biological and medical sciences; Biology; Cell Differentiation; Cell separation; cells; Cellular metabolism; cellule; celulas; crecimiento; croissance; Developmental biology; Dictyostelium; Dictyostelium - physiology; diferenciacion celular; differenciation cellulaire; Embryos; Enzymes; enzymic activity; expresion genica; expression des genes; Fundamental and applied biological sciences. Psychology; gene expression; Gene Expression Regulation, Enzymologic; growth; Hexanones - metabolism; Invertebrates; Lyases - analysis; Messenger RNA; mixomicetes; moho; moisissure; Mollusks; morfogenesis; morphogenese; morphogenesis; moulds; myxomycetes; Oxidoreductases; Physiological regulation; Protozoa; RNA, Messenger - analysis; Slugs; Spores; Time Factors; Tissue Distribution; Dictyostelium discoideum; Protozoa; Regeneration; Gradient; Enzyme; Morphology; Development; Isolation; Differentiation; Localization; Mycetozoa
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.90.2.487

Differentiation-inducing factor 1 [DIF-1; 1-(3,5-dichloro-2,6-dihydroxy-4-methoxyphenyl)-hexan-1-one] induces stalk cell differentiation during Dictyostelium development. It is present as a gradient in the multicellular slug, its lowest concentration being in the anterior. Here we demonstrate the existence of a localized sink for DIF-1, also in the anterior of the slug, which could be responsible for generating the DIF-1 gradient. DIF-1 is metabolized extensively by developing cells, initially by a mono-dechlorination. We used an enzyme assay for DIF-1 dechlorinase to examine its distribution in the slug. DIF-1 dechlorinase activity is 30-fold higher in prestalk cells (largely anterior) compared with prespore cells (posterior) when these are separated from each other on Percoll density gradients. Dissection experiments showed that DIF-1 dechlorinase is 25-fold enriched in the anterior 13% of the slug compared with the rest. These experiments also showed that DIF-1 dechlorinase is more anterior-enriched than the standard prestalk markers, the ecmA and ecmB mRNAs. When cut from a slug, both prestalk and prespore fragments regulate to restore the missing cell type. Prespore fragments rapidly regain (by 30 min) a DIF-1 sink in their anteriors, and prestalk fragments restore a posterior zone with low DIF-1 dechlorinase by 4 hr after cutting. The reappearance of the DIF-1 sink in the anterior of prespore fragments is accomplished without detectable cell sorting and may, therefore, be in response to positional signals. Finally, a localized sink may provide a general way of producing a gradient of a signal substance in a developing embryo.