Fitness assays of the engineered <i>Sc/Su</i> hybrids carrying different type of <i>TRP2/TRP3</i> chimeric complexes.

<p><i>Sc/Su</i> hybrids were genetically modified to carry either the two different chimeric complexes, Trp2p<sup>Su</sup>/Trp3p<sup>Sc</sup> and Trp2p<sup>Sc</sup>/Trp3p<sup>Su</sup>, or the two parental hemizygous controls, Trp2p<sup>Su</sup>/Trp3p<sup>Su</sup> and Trp2p<sup>Sc</sup>/Trp3p<sup>Sc</sup> (panel A). The growth curves of <i>S. cerevisiae</i>, <i>S. uvarum</i>, the hybrid <i>Sc/Su</i> and the engineered hybrids shows that Trp2p<sup>Su</sup>/Trp3p<sup>Sc</sup> grows better than the other combinations in SD media lacking tryptophan (panel B). The fitness competition assay between <i>Sc/Su</i> hybrids with different combination of the <i>TRP2/TRP3</i> complex and the GFP reference strain shows again that Trp2p<sup>Su</sup>/Trp3p<sup>Sc</sup> 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).</p>