Fig. 4. Expression of the CTS gene. (A) Total RNA was extracted from wild-type (AW303-2b), Δcbk1 (WR03-5d), Δace2 (WR27-1a) Δcbk1 dominant suppressor (5d2) and Δcbk1 recessive suppressor (5d1) strains. Aliquots of 10 µg were used in a northern analysis, probed with CTS1, the ACT1 gene was used as an internal standard. CTS1 transcription is almost undetectable in the Δcbk1 and Δace2 strains but is re-established in the suppressor strains. (B) Haploid strains with a deleted CBK1 gene derived from W303 (WR05-5a) and S288c (WR208-1a) were transformed by a plasmid where the expression of the CTS1 gene is under the control of the GAL promotor (YEpWJR064). Transient expression of chitinase on galactose medium causes the large aggregates associated with the deletion of the CBK1 gene to separate.