Figure 1. A population-based growth phenotype in yeast.

(a, upper row) WT haploid MATa yeast exhibits a pica phenotype, which is only observable after transformation with pQ56 (right column) but not in control transformations with pQ0 (left column) and pQ30 (middle column). Size differences between Q₅₆-YFP expressing yeast and the Q₀ and Q₃₀ controls become obvious in differential interference contrast (DIC) microscopy (lower row). The scale bar represents 10 mm in the upper row and 5 μm in the lower row. (b) Analysing the cellular cross-section area for the predominant colony type, pQ56-transformants exhibit a subpopulation of cells of a larger size (n=740, n=659 and n=769 for pQ0, pQ30 and pQ56, respectively; Supplementary Fig. 3 for further biological replicates). (c) FACS analysis of WT MATa reveals a higher incidence of 2N and 4N cells in response to pQ56 transformation (red) compared with pQ0 (black) and pQ30 (blue). (d) Transforming diploid WT MATa/α and WT MATα shows that the pica phenotype is conserved in the MATα genetic background but absent in the diploid strain. (e) In FACS, WT MATα still exhibits a mainly haploid state and an enrichment in 2N and 4N states after pQ56 transformation. (f) The diplod WT MATa/α strain transformed with pQ0 (black), pQ30 (blue) and pQ56 (red), however, shows an equal shift to the 2N and 4N positions for all polyQ constructs.