Poster_ENBE14 printing version v2_LP_CX_GE_LP
- 1. Experimental Protocol Differences in mutation accumulation in Schyzosaccharomyces pombe due to the presence of chromosomal rearrangements Gustavo Eduardo, Simone Delgado, Ana Paula Marques, Lília Perfeito Evolution and Genome Structure Group – Instituto Gulbenkian de Ciência, Rua da Quinta Grande, 6, Oeiras, Portugal Large chromosomal rearrangements are common in natural populations and thought to be involved in speciation events. In this project, we used experimental evolution to determine how the speed of evolution and the type of accumulated mutations depend on the ancestral chromosomal structure and genotype. We utilized two Wild Type strains and a set of genetically engineered Schizosaccharomyces pombe strains (Avelar, 2012), different solely in the presence of a certain type of chromosomal variant (one inversion and four translocations), along with respective controls. These strains were propagated in the laboratory at very low population sizes, in which we expect natural selection to be less efficient at purging deleterious mutations (Gordo et al, 2011). We then measured these strains’ changes in fitness throughout this accumulation of deleterious mutations, comparing the evolutionary trajectories in the different rearrangements to test if the chromosomal structure affected the speed of evolution. Our data indicates that different genetic backgrounds accumulate mutations at different rates, even when natural selection is very weak. Certain chromosomal rearrangements bias the accumulation of mutations towards beneficial mutations, conferring the strain that carries them an adaptive advantage. Results Conclusions • The genomic background affects it’s potential evolutionary path, even when minimizing environmental and natural selection effects. • Surprisingly, all T4 replicates and some replicates of C2 and C5 presented increases in fitness. • Is there selection even at low population sizes? • Could one of the strains be exceptionally prone to high effect beneficial mutations? Bibliography/Reference Avelar A; Chromosomal structure: a selectable trait for evolution. Instituto de Tecnologia Química e Biológica, Oeiras, November 2012 Gordo I, Perfeito L, Sousa A; Fitness Effects of Mutations in Bacteria. J Mol Microbiol Biotechnol 2011;21:20–35 Acknowledgments Funding for this project was provided by Different strains accumulate mutations at different speeds EXPL/BIA-EVF/0129/2013 * - significant change in fitness distributions between both bottleneck numbers Δ - significant change in fitness average. */Δ p-value < 0.05; **/Δ Δ p-value < 0.01; ***/Δ Δ Δ p-value < 0.001 (Statistical significance tested with the Kolmogorov-Smirnov and Mann–Whitney–Wilcoxon tests) mCherry-marked S. pombe 48 hours later 1st Bottleneck (…) 144th Bottleneck (B144) Mutation Accumulation Experiment Statistical analysis Fluorescence-activated cell sorting (FACS) Rich medium (1mg/mL ampicillin) x12 lines per strain Plus controls for each rearrangement. Ex: Ancestral Strains: 2 Wild Type Karyotypes 5 Chromossomal Rearrangents Reference Strain BD LSRFortessa™ cell analyzer Competition Assay Results from fitting an Analysis of Variance Model (ANOVA) comparing ∆W (fitness at B144 subtracted from fitness at B0) of all lines from different genomic backgrounds. Red indicates p-value < 0.05, yellow indicates 0.01 > p-value > 0.001 and green indicates 0.001 > p- value. Bonferroni corrections were applied to all p-values. SPP26 SPP27 I2 C2 T4 C4 T5 C5 T8 C8 T10 C10 SPP26 SPP27 9,8977E-09 I2 5,36628972 2,1E-06 C2 32,176518 6,227178 50,15595 T4 1,5832E-10 3,29E-15 6,99E-10 0,847641 C4 37,8229896 9,15E-10 1,297978 30,13474 1,89E-14 T5 0,15037645 6,15E-07 24,05454 59,73462 8,47E-14 0,00212 C5 13,4667456 0,000323 62,64657 51,60644 3,47E-06 8,015205 39,11081 T8 9,3140652 6,9E-09 26,31535 42,04811 1,53E-14 0,273657 1,073373 35,86171 C8 62,1447156 2,23E-08 5,511067 35,1945 5,8E-12 25,44505 0,069723 15,66261 6,039258 T10 36,8132622 9,9E-09 11,22059 36,34719 6,96E-12 10,89927 0,370212 21,34037 23,6161 37,01266 C10 57,6936096 5,1E-10 2,290222 31,08003 1,84E-14 32,49946 0,006733 10,21945 1,431345 49,90801 22,89706