J. G. Williams

Learn More
Molecular genetic maps are commonly constructed by analyzing the segregation of restriction fragment length polymorphisms (RFLPs) among the progeny of a sexual cross. Here we describe a new DNA polymorphism assay based on the amplification of random DNA segments with single primers of arbitrary nucleotide sequence. These polymorphisms, simply detected as(More)
The ecmA (pDd63) and ecmB (pDd56) genes encode extracellular matrix proteins of the slime sheath and stalk tube of Dictyostelium discoideum. Using fusion genes containing the promoter of one or other gene coupled to an immunologically detectable reporter, we previously identified two classes of prestalk cells in the tip of the migrating slug; a central core(More)
The ecmA gene of Dictyostelium encodes an extracellular matrix protein and is selectively expressed in prestalk cells. We show that its promoter contains discrete elements that direct expression in different subpopulations of prestalk cells. Prestalk(pst)A cells occupy the front half of the prestalk region. Expression in pstA cells requires DNA sequences(More)
An approach to isolating DNA sequences that are linked to important plant genes is described. The strategy is based upon a recent modification of the polymerase chain reaction in which synthetic primers are used to amplify random sequences from genomic DNA. This technique, used in conjunction with near-isogenic lines (which differ only by the presence or(More)
The characteristic structure of the mature Dictyostelium culminant is created by the regionalized cellular differentiation and directed movement of prestalk cells. The front prestalk zone of the migratory slug has previously been considered to be a homogeneous tissue. Here we demonstrate, however, the existence of multiple classes of prestalk cells located(More)
The TTGA-binding factor is a transcriptional regulator activated by DIF, the chlorinated hexaphenone that induces prestalk cell differentiation in Dictyostelium. The same activity also functions as a repressor, controlling stalk cell differentiation. We show that the TTGA-binding factor is a STAT protein. Like the metazoan STATs, it functions via the(More)
Using cell-autonomous markers we have traced the origins of prespore cells and two types of prestalk cells (pstA and pstB cells) during slug formation. We show that cell sorting and positional information both contribute to Dictyostelium morphogenesis. The initial pattern established at the mound stage is topologically quite different from that of the slug.(More)
We present evidence that Dictyostelium slug tip cells, the pstA cells, may arise by positional differentiation, but at a site remote from that which they will eventually occupy. When first detectable, the pstA cells form a peripheral ring surrounding the other prestalk cell subtype, the pstO cells, but subsequently move above the pstO cells to form the tip.(More)
Dd-STAT, the protein that in part controls Dictyostelium stalk cell differentiation, is a structural and functional homolog of metazoan signal transducers and activators of transcription (STATs). Although present during growth and throughout development, Dd-STAT's tyrosine phosphorylation and nuclear localization are developmentally and spatially regulated.(More)