Expression of GUS in Prom280:GUS and Prom290:GUS plants in response to temperature treatments. Ten-day-old plants were grown on MS agar plates photoautotrophically at 21°C, and incubated for 48 h at 37°C and 4°C. GUS staining of Prom280:GUS and Prom290:GUS plants before (A and B) and after transferring the plants to higher (37°C, C and D) or lower (4°C, E and F) temperature conditions. GUS activity was quantified in whole aerial part using 4-methylumbelliferone [MU] as substrate, and results are reported in a relative scale (G and H). Control of Prom280:GUS line was 6.52 ± 1.04 nmoles MU/min/mg protein, and control of Prom290:GUS line was 76.56 ± 18.84 nmoles MU/min/mg protein. Each point represents a single replicate. Asterisks (**) indicate significant differences between treatments and controls according to Student's t-Test at P < 0.005. Plants transformed with pBI101.1 (I). Roots of Prom290:GUS line after heat treatment (37°C) (J).