Fig 1.

Drop tests comparing growth of yeast strains W303-1A and YPC-1 on galactose and glucose (A) and genomic analysis of conditional mutant strain YPC-1 by Southern blot (B) and PCR (C). Cells were grown to saturation in galactose medium and transferred to glucose for 18 h to stop the transcription of IPP1; then, serial dilutions of the cultures (10²-, 10³-, and 10⁴-fold) were made in sterile water, and 10 μl of each of the dilutions were spotted onto agar plates containing medium with galactose or glucose as carbon sources. Growth was recorded after 5 days. For Southern blot, DNA preparations from strains W303-1A (lane 1), W303-1A transformed with plasmid pYPC1 (lane 2), and YPC-1 (lane 3) were processed as described in Materials and Methods. An EcoRV 675-bp-long DNA fragment containing approximately two-thirds of S. cerevisiae IPP1 coding sequence was used as a probe. PCRs were performed using DNA from the same strains as templates and oligonucleotides corresponding to the full-length IPP1 coding sequence as primers. Samples were run in a 0.7% agarose gel, and resulting DNA bands were visualized with ethidium bromide.