Figure 1.

Basal and acquired thermotolerance of etiolated seedlings of tomato wild-type and HsfA2 transgenic lines. A, Relative gene expression (2^–ΔΔCt) of HsfA2, Hsp17.7C-CI, and Hsp101 in wild-type and A2AS transgenic seedlings kept at 25°C (control, sample C) or exposed to 1 h HS at 39°C (sample H), which was followed by recovery for 1.5 h at 25°C (sample R). The Ct value for each gene was normalized to Ct values for EF1α and UBI housekeeping genes and to expression in wild-type control. Vertical bars are the average ± sd of three replicates. B, Four-day-old etiolated tomato wild-type and A2AS-3, -7, and -15 transgenic seedlings were exposed to 39, 42, or 45°C for 90 min. Hypocotyl length was recorded for 5 d after stress and growth rate was calculated. C, Same seedlings as in B were exposed to 37.5°C for 90 min and then allowed to recover at 25°C for 3 or 24 h. Following recovery, a severe HS at 47.5°C for 90 min was applied. Hypocotyl length was recorded for 5 d after stress, and growth rate was calculated. Pictographs on the right in B and C indicate the applied HS regimes, respectively. Each data point is the mean ± se of at least 10 seedlings for each genotype and treatment. For A and C, asterisk denotes significant difference (P < 0.05) compared to the wild type for a given sample or stress treatment as shown by pairwise t test analyses.