The SPR6, EST2, BUB3 and TBF1 orthologs from the genomes of S. paradoxus, S. mikatae, S. bayanus, S. castellii, S. kudriavzevii and S. kluyveri were extracted from the Yeast Gene Order Browser (http://wolfe.gen.tcd .ie/ygob/) (28) . Orthologs were identified for all genes. The nucleotide sequences were analyzed for the presence of potential À1 RF signals as previously described (15, 17) . Results are compiled in Supplementary Table S4 .