Fig. 1.

Construction and testing of heterozygous diploid strains. a Experimental workflow. A S. cerevisiae strain bearing one or more synthetic chromosomes is mated to a S. cerevisiae or S. paradoxus strain with a “wild-type” genome. The resultant heterozygous diploid cells can be selected for, SCRaMbLEd, and tested for tolerance of a variety of environmental and chemical conditions. Strains showing increased fitness have their phenotype verified and can be analyzed with whole genome sequencing to determine the sets of SCRaMbLE events responsible for a given phenotype. b SCRaMbLE of haploid and heterozygous diploid synVsynX yeast was induced by adding 1 µM β-estradiol to culture media for 6 h. Heterozygous diploid S288C-synVsynX strains demonstrate a lesser degree of SCRaMbLE-mediated lethality at both 30 °C and 37 °C compared to haploid synVsynX strains. c Heterozygous diploid strains incorporating a variety of S. cerevisiae “wild-type” genomes are robust to SCRaMbLE. Additionally, heterozygous diploid strains containing two synthetic chromosomes can be SCRaMbLEd without appreciable loss in viability compared to strains containing one synthetic chromosome