HSF and heat shock-induced gene expression is similar in wild-type and siz1 seedlings. Ten-day-old wild-type and siz1-2 seedlings were exposed to 37°C for the times indicated. Transcript abundance was determined by semiquantitative reverse transcription-PCR for four major HSFs (HSF1, 3, 4, and 7), and five different HSPs (HSP17.6A [class II sHSP], HSP18.2 [class I sHSP], HSP70, HSP83.1, HSP101) and APX1 and APX2. Black arrows indicate the period of heat shock.