<it>Gdt</it>2 regulates the transition of <it>Dictyostelium </it>cells from growth to differentiation

• Main Authors: Anjard Christophe, Chibalina Margarita V, Insall Robert H
• Format: Article
• Language: English
• Published: BMC 2004-07-01
• Series: BMC Developmental Biology
• Online Access: http://www.biomedcentral.com/1471-213X/4/8

<p>Abstract</p> <p>Background</p> <p><it>Dictyostelium </it>life cycle consists of two distinct phases – growth and development. The control of growth-differentiation transition in <it>Dictyostelium </it>is not completely understood, and only few genes involved in this process are known.</p> <p>Results</p> <p>We have isolated a REMI (restriction enzyme-mediated integration) mutant, which prematurely initiates multicellular development. When grown on a bacterial lawn, these cells aggregate before the bacteria are completely cleared. In bacterial suspension, mutant cells express the developmental marker discoidin Iγ even at low cell densities and high concentrations of bacteria. In the absence of nutrients, mutant cells aggregate more rapidly than wild type, but the rest of development is unaffected and normal fruiting bodies are formed. The disrupted gene shows substantial homology to the recently described <it>gdt</it>1 gene, and therefore was named <it>gdt</it>2. While GDT1 and GDT2 are similar in many ways, there are intriguing differences. GDT2 contains a well conserved protein kinase domain, unlike GDT1, whose kinase domain is probably non-functional. The <it>gdt</it>2 and <it>gdt</it>1 mRNAs are regulated differently, with <it>gdt</it>2 but not <it>gdt</it>1 expressed throughout development. The phenotypes of <it>gdt</it>2^-and <it>gdt</it>1^-mutants are related but not identical. While both initiate development early, <it>gdt</it>2^-cells grow at a normal rate, unlike <it>gdt</it>1^-mutants. Protein kinase A levels and activity are essentially normal in growing <it>gdt</it>2^-mutants, implying that GDT2 regulates a pathway that acts separately from PKA. <it>Gdt</it>1 and <it>gdt</it>2 are the first identified members of a family containing at least eight closely related genes.</p> <p>Conclusions</p> <p>We have isolated and characterised a new gene, <it>gdt</it>2, which acts to restrain development until conditions are appropriate. We also described a family of related genes in the <it>Dictyostelium </it>genome. We hypothesise that different family members might control similar cellular processes, but respond to different environmental cues.</p>