Figure 2.

(A) Physical maps of the CHS4 and BNI4 regions and structures of the chs4-Δ1 and bni4-Δ1 deletion alleles. Open boxes represent open reading frames, and stippled boxes represent the TRP1 gene plus flanking sequences. Arrows indicate the directions of transcription. Solid black bars represent the fragments used to probe DNA blots. Lines beneath the CHS4 map represent segments of DNA assayed (in the indicated low-copy plasmids) for complementation of the synthetic lethality of strain DDY156 or 124Y03A (SL) and of the chitin synthesis defect of the chs4-Δ1 strain DDY174 (CS); AA indicates the COOH-terminal Chs4p amino acid encoded by the corresponding DNA. Restriction enzymes: G, BglII; H, HindIII; N, NsiI; R, EcoRI; S, SalI; Sa, Sau3AI; Sp, SphI; V, EcoRV; X, XbaI. There are other Sau3AI sites in the BNI4 region; those indicated represent the ends of the insert in plasmid p356 (see text). (B) DNA–DNA blot-hybridization analyses of chs4-Δ1 and bni4-Δ1 strains. Genomic DNAs were digested with HindIII. Lanes 1–6 were probed with a 2.9-kb BglII–HindIII fragment that contains most of CHS4 and some upstream DNA (see A). Lanes 7–12 were probed with a 2-kb EcoRV fragment that contains a portion of BNI4 and some downstream DNA (see A) together with a portion of the tet^R gene of YEp13. Lanes 1 and 7, YEF473 (wild-type); lanes 2 and 8, DDY176 (chs4-Δ1/CHS4 bni4-Δ1/BNI4); lanes 3–6 and 9–12, the four segregants from one tetratype tetrad from DDY176. Fragments of the predicted sizes were visualized in all lanes (note the presence of a HindIII site in TRP1); their molecular weights are indicated in kb.