Table 1 Yeast stains used in this study

Strain	Mating type	Markers	Source
C+	MATalpha	no auxotrophic markers	Brambilla 1999^{^a}
C+ rho-zero	MATalpha	no mtDNA	this paper
*C+ afo1^-*	MATalpha	afo1::Nourseo^R ATP3^G348T	this paper ^{^b}
C+ MATa	MATa	no auxotrophic markers	this paper
JS760	MATa/alpha	afo1::Nourseo^R/AFO1⁺ ATP3^G348T/ATP3⁺	this paper
JS760-6A	MATa	AFO1⁺ ATP3^G348T	this paper
JS760-6B	MATa	afo1::Nourseo^R ATP3⁺	this paper
JS760-6C	MATalpha	AFO1⁺ ATP3⁺	this paper
JS760-6D	MATalpha	afo1::Nourseo^R ATP3^G348T	this paper
JS765	MATa/MATalpha	a cross of 6Bx6D	this paper
*C+ ura3^-*	MATalpha	ura3^-	a gift from D.Porro
*JS760-6B his3^-*		same markers as JS760-6B, but his3::kanMX4	this paper

↵a strain GRFc of Brambilla et al. 1999 was renamed C+ for the purpose of the present paper.
↵b The mutation ATP3^G348T in this strain ocurred spontaneously and was discovered during the course of this work.