Genetic Architecture of Micro-Environmental Plasticity in Drosophila melanogaster

Abstract

Individuals of the same genotype do not have the same phenotype for quantitative traits when reared under common macro-environmental conditions, a phenomenon called micro-environmental plasticity. Genetic variation in micro-environmental plasticity is assumed in models of the evolution of phenotypic variance, and is important in applied breeding and personalized medicine. Here, we quantified genetic variation for micro-environmental plasticity for three quantitative traits in the inbred, sequenced lines of the Drosophila melanogaster Genetic Reference Panel. We found substantial genetic variation for micro-environmental plasticity for all traits, with broad sense heritabilities of the same magnitude or greater than those of trait means. Micro-environmental plasticity is not correlated with residual segregating variation, is trait-specific, and has genetic correlations with trait means ranging from zero to near unity. We identified several candidate genes associated with micro-environmental plasticity of startle response, including Drosophila Hsp90, setting the stage for future genetic dissection of this phenomenon.

Figure 1. Stackplots showing variation in ln(σ_E) among DGRP lines for females (red) and males (blue)

(a) Chill coma recovery time. (b) Startle response. (c) Starvation stress resistance.

Figure 2. Correlations of mean and micro-environmental variance of three quantitative traits for females (red) and males (blue)

(a) Chill coma recovery time. The correlations between the mean and micro-environmental variance (r_MV) and r_MV= 0.79 (P < 0.0001) for females and r_MV= 0.80 (P < 0.0001) for males. (b) Startle response. r_MV= −0.12 (P = 0.10) (females), r_MV= −0.03 (P = 0.70) (males). (c) Starvation resistance. r_MV= 0.50 (P < 0.0001) (females), r_MV= 0.50 (P < 0.0001) (males).

Figure 3. Molecular variants associated with ln(σ_E) of startle response in or near (±1 kb) Hsp83 for females (red) and males (blue)

The physical position of variants is indicted by their relative spacing on the x-axis. The y-axis gives –log10(P-values) for each variant. The dashed line gives the Bonferroni and the dotted line the FDR thresholds corresponding to an experiment-wise P-value of 0.05. Two variants met the Bonferroni threshold: 3L_3191981_SNP (in the exon of CG14965 and 989 bp upstream of Hsp83) and 3L_3193430_SNP (in the first exon of Hsp83). The remaining four variants met the FDR threshold: 3L_3192162_SNP (in the exon of CG14965 and 808 bp upstream of Hsp83); 3L_3192350_SNP (in the exon of CG14965 and 619 bp upstream of Hsp83); 3L_3192548_SNP (58 bp upstream of CG14965 and 422 bp upstream of Hsp83) and 3L_3193101_SNP (in the first exon of Hsp83).