Fitness assays of the engineered Sc/Su hybrids carrying different type of TRP2/TRP3 chimeric complexes.
Sc/Su hybrids were genetically modified to carry either the two different chimeric complexes, Trp2pSu/Trp3pSc and Trp2pSc/Trp3pSu, or the two parental hemizygous controls, Trp2pSu/Trp3pSu and Trp2pSc/Trp3pSc (panel A). The growth curves of S. cerevisiae, S. uvarum, the hybrid Sc/Su and the engineered hybrids shows that Trp2pSu/Trp3pSc grows better than the other combinations in SD media lacking tryptophan (panel B). The fitness competition assay between Sc/Su hybrids with different combination of the TRP2/TRP3 complex and the GFP reference strain shows again that Trp2pSu/Trp3pSc grows faster (panel C). The competitive fitness coefficient Sg represents the difference between the ln of the ratio of hybrid and reference strain between final and initial time points, normalized for the number of generations. An equal fitness between hybrid and reference strains would be indicated by a value of zero (see Method section).