Revertants of pleiotropic cross resistance and collateral sensitivity in yeast: A multivariate analysis

Abstract

Five different selective media (Table 2) were used to isolate revertants of a pleiotropic cross resistant and collaterally sensitive strain of yeast. Of the 2676 revertants isolated, 1542 were visually classified as complete revertants, 238 as dauermodifications and 896 as partial revertants. Growth of the 896 partial revertants was evaluated on 24 diagnostic media (Table 1). Multivariate classification of revertant growth (Fig. 1) arranged the revertants into 9 groups and the media into two major groups (Table 4). The identification of two groups of media was consistent with the notion of a single gene alteration of mitochondrial and plasma membrane function in the original mutant strain. The 9 revertant groups had phenotypes suggesting pseudo-wild type (1 group), pseudo-mutant type (2 groups), loss of collateral sensitivity (2 groups), loss of cross resistance (1 group) and loss of different aspects of the resistance phenotype (3 groups). One of the latter 3 groups had a phenotype similar to strains reported by Guerineau et al. (Biochem. Biophys. Res. Commun. 61, 462) to be deficient in 2 μ DNA. The five media used to select revertants enriched for different groups within the 9 different groups of revertants (Table 5). The multivariate analyses used in this paper would be of general use in the analysis of other complex pleiotropic phenotypes.