Heat triggers a general inhibition of protein synthesis.

<p>(<b>A</b>) Metabolic labeling of <i>de novo</i> synthesized proteins from Arabidopsis seedlings grown at 22°C or after a heat shock of 38°C during the indicated times. High molecular weight heat-shock proteins are indicated by an asterisk. (<b>B</b>) Verification of the quality of the polysome preparation. Equal volumes of the last 16 fractions of the sucrose gradient from control or heat-stressed Arabidopsis seedlings were subjected to electrophoretic analysis. According to the distribution of 18 S and 28 S rRNAs, fractions 1–8 were designated as non-polysomal (NP), while fractions 11–16 were considered as polysomal (HP) fractions. (<b>C</b>) Quantification and graphic representation of the polysome profiles from the samples in (B). (<b>D</b>) Polysome content (PC) of control or heat-stressed Arabidopsis seedlings was calculated as described in materials and methods. Values are mean percentages from three biological samples (*P<0.05).