Project description:We identified 3418 genes transcribed at a level of at least two copies each. We identified many transcripts involved in protein translation, cell maintenance and metabolism, as expected for vegetative cells. The most highly expressed cell signaling genes include ubiquitin, smlA, and nucleotide exchange factors RasGEF F and Ras GEF G. Additionally, we identified many genes previously reported to be expressed only during later stages of development including dutA, actin8, thioredoxin3, culmination specific protein 45D, discoidin II and yelA. We isolated total RNA from Dictyostelium amoeba growing in HL5 media with shaking and at a density of 2.4 X 10(7) cells/ml using Ambion RNAqueous isolation kit. We prepared the SAGE library using an Invitrogen kit and being careful to reduce the amount of ditags in the concatemer ligation reaction to 25% of the manufacturer's suggested mass. Concatemers were sequenced at the Molecular Research Core Facility on the campus of Idaho State University using an Applied Biosystems 3100 Genetic Analyzer. We identified SAGE tags by comparison to the Dictyostelium genome sequence available on the dictybase website.
Project description:We identified 3418 genes transcribed at a level of at least two copies each. We identified many transcripts involved in protein translation, cell maintenance and metabolism, as expected for vegetative cells. The most highly expressed cell signaling genes include ubiquitin, smlA, and nucleotide exchange factors RasGEF F and Ras GEF G. Additionally, we identified many genes previously reported to be expressed only during later stages of development including dutA, actin8, thioredoxin3, culmination specific protein 45D, discoidin II and yelA.
Project description:Upon starvation, Dictyostelium discoideum cells halt cell proliferation, aggregate into multicellular organisms, form migrating slugs, and undergo morphogenesis into fruiting bodies while differentiating into dormant spores and dead stalk cells. At almost any developmental stage cells can be forced to dedifferentiate when they are dispersed and diluted into nutrient broth. However, migrating slugs can traverse lawns of bacteria for days without dedifferentiating, ignoring abundant nutrients and continuing development. We now show that developing Dictyostelium cells revert to the growth phase only when bacteria are supplied during the first 4 to 6 h of development but that after this time, cells continue to develop regardless of the presence of food. We postulate that the cells' inability to revert to the growth phase after 6 h represents a commitment to development. We show that the onset of commitment correlates with the cells' loss of phagocytic function. By examining mutant strains, we also show that commitment requires extracellular cyclic AMP (cAMP) signaling. Moreover, cAMP pulses are sufficient to induce both commitment and the loss of phagocytosis in starving cells, whereas starvation alone is insufficient. Finally, we show that the inhibition of development by food prior to commitment is independent of contact between the cells and the bacteria and that small soluble molecules, probably amino acids, inhibit development during the first few hours and subsequently the cells become unable to react to the molecules and commit to development. We propose that commitment serves as a checkpoint that ensures the completion of cooperative aggregation of developing Dictyostelium cells once it has begun, dampening the response to nutritional cues that might inappropriately block development.
Project description:Differential expression of Dictyostelium discoideum AX2 upon infection with wt L. pneumophila JR32 vs. uninfected 24h p.i. (timecourse experiment)
Project description:Differential expression of Dictyostelium discoideum AX2 upon infection with wt L. pneumophila JR32 vs. uninfected 48h p.i. (timecourse experiment)