Extended Data Fig. 9. Ectopic expression of TWA1 enhances thermotolerance but does not affect growth and photosynthesis.
a, TWA1 transcript levels in two representative TWA1-overexpressing (TWA1oe) lines in comparison to wild type and the twa1 mutants. 5-d old seedlings were analysed for TWA1 transcript abundance by RT-qPCR with UBC9, UBI10 and TIP41L transcripts as reference. Ectopic TWA1 expression was under the control of the viral 35 S promoter in twa1-2 mutant background. The TWA1 transcript level in wild type (pHB6:LUC) was set to 1 and fold change of abundance in mutants and TWA1oe lines is presented. Data are mean ± SD, n = 3, ten seedlings per n. b, Enhanced acquired thermotolerance of TWA1oe lines. Inhibition of root growth in TWA1oe lines (red) compared to WT in response to various 45 °C exposure times (mean ± s.d., n = 6). c, Basal thermotolerance is improved in TWA1oe lines and impaired in twa1-1 and twa1-2. Chlorophyll content per fresh weight of 5d-old seedlings one day after exposure to 37 °C as indicated (mean ± s.d., n = 15 from three repetitions). The chlorophyll content at t = 0 was set to 1. d, e, Improved thermotolerance of TWA1oe lines without tradeoffs in growth and changes in apparent photosynthetic parameters. Comparison of total leaf area (leaf area; n = 4), leaf temperature (Tleaf; n = 4), net photosynthesis (An; n = 7), transpiration (E; n = 7), and stomatal conductance (gs; n = 7) of plants grown for 38 days at short-day conditions with 22 °C daytime temperature and 150 µmol m−2 s−1 photosynthetic active radiation (mean ± s.e.m.). e, 20-day-old plantlets analysed for maximum quantum efficiency of photosystem II (FPSIImax), quantum efficiency of photosystem II (FPSII), and non-photochemical quenching (NPQ). No statistically significant differences were found (n = 9; P > 0.05, one-way ANOVA). Left, Values are expressed in false colours. Right, mean ± s.e.m. Statistical analysis for b-e is provided in SI Extended Data Fig. 9.