Heterologous Hsp90 promotes phenotypic diversity through network evolution
Fig 2
Evolving Ylip-HSP90 lines fix the first beneficial mutations more quickly and have better fitness improvements.
(A) Experimental evolution for adaptation to a heterologous Hsp90. Twelve Ylip-HSP90 evolving lines and 12 Scer-HSC82 control lines were set up to evolve in rich media at 28°C. Two isogenic subpopulations (red: DsRed-labeled subpopulation; green: GFP-labeled subpopulation) were mixed in an approximate ratio of 1:1 in the initial cultures. The subpopulation that obtained a beneficial mutation (noted by a star) would start expanding its frequency in the evolved culture. (B) The Ylip-HSP90 lines become fixed more quickly than the Scer-HSC82 lines. The mutation fixation of each culture was determined as the time when the frequency of a subpopulation was observed to be greater than 95% according to flow cytometry. The control line con6 and the evolving lines, evo1, evo2, and evo12 were excluded because of culture contamination during evolution. The frequency dynamics of each evolved line are shown in S3 Fig. (C) Evolved Ylip-HSP90 populations have enhanced fitness improvements compared with evolved Scer-HSC82 populations in YPD at 28°C (p-value = 4.54 × 10−7, t = −7.97, df = 15, one-tailed Student t test, unequal variance; data did not deviate from the normal distribution, Shapiro-Wilk test). Cells were grown in liquid cultures and growth rates were measured by plate readers. Fitness improvement was calculated according to the formula [(fitness of the evolved culture/fitness of the ancestral strain) − 1] × 100%. Error bars are standard errors, N ≥ 4. The numerical data used in panels (B, C) are included in S1 Data. DsRed, red fluorescent protein; GFP, green fluorescent protein; Scer, Saccharomyces cerevisiae; Ylip, Yarrowia lipolytica; YPD, Yeast extract-Peptone-Dextrose.