Figure 2. Comparison of heat-induced changes in steady-state and polysome bound mRNAs from Arabidopsis seedlings.

(A) Illustration of the experimental design. Total and polysome-bound mRNA from control or heat-stressed seedlings were isolated in parallel for microarray hybridization to Arabidopsis whole-genome Affymetrix ATH-1 platform and subsequently analyzed. (B) Graphic representation of the number of mRNAs with ≥2-fold variations in steady-state levels (mRNA_TOT) or in polysome association (mRNA_PB) in response to the heat treatment. Green and red colors represent upregulated and downregulated mRNAs under heat stress, respectively. (C) Venn diagrams of heat-stress upregulated and downregulated mRNAs. mRNAs that only experienced significant variations in steady-state levels (≥2-fold variations in mRNA_TOT, FDR<0.05) are shown in blue, those that only experienced significant changes in their association to polysomes (≥2-fold variations mRNA_PB, FDR<0.05) are shown in red. Merged section included those transcripts that significantly changed at both, transcriptional and translational, levels (≥2-fold variations in mRNA_TOT and mRNA_PB, FDR<0.05) in response to the heat treatment. (D) Genome-wide comparison of the heat-induced changes in the transcriptome (x-axis, log₂ΔmRNA_TOT) and the translatome (y-axis, log₂ΔmRNA_PB). The log_2-values of the fold changes were plotted for all the probe sets included in the Affimetrix ATH-1 microarray (n = 22810). mRNAs with an average translation efficiency (log₂ΔmRNA_PB/ΔmRNA_TOT) are shown in blue, while mRNAs with ≥1.5 or ≤1.5 fold the average translation efficiency are shown in green and red, respectively.