Fig. 5: ELF3-dependent thermal regulation of PIF4 activity.

a Iodine staining showing the starch contents of 4-d-old Col-0 and elf3-1 seedlings grown under 50 μmol m⁻² s⁻¹ R light during the 21–27 °C transition. b Images of 4-d-old Col-0 and elf3-1 seedlings grown at either 21 or 27 °C without (-s) or with (+s) sucrose. c Hypocotyl length measurements of the Col-0 and elf3-1 seedlings described in (b). Error bars for the hypocotyl measurements represent the s.e. (n = three biological replicates), and the centers of the error bars indicate the mean. The magenta bars show the relative response, which is defined as the hypocotyl response of a mutant at 27 °C relative to that of Col-0 (set at 100%). The relative thermal responses for elf3-1 without or with sucrose are shown. Different letters denote statistically significant differences in the relative response (one-way ANOVA, Tukey’s HSD, p < 0.05, n = 3 biological replicates). elf3-1 seedlings treated with sucrose grown at 21 °C were slightly taller than Col-0 grown at 27 °C, but the difference was within twofold and therefore considered not significant (n.s, two-tailed Student t-test). d Immunoblot analysis of the PIF4 levels in 4-d-old Col-0 and elf3-1 seedlings grown under 50 μmol m⁻² s⁻¹ R light without or with sucrose during the 21–27 °C transition. Actin was used as a loading control. The relative PIF4 levels normalized to the corresponding levels of actin are shown. e Quantification of the PIF4 levels shown in (d). Error bars represent the s.d. (n = four biological replicates), and the centers of the error bars indicate the mean. f qRT-PCR analysis of the PIF4 transcript levels in 4-d-old Col-0 and elf3-1 seedlings grown under 50 μmol m⁻² s⁻¹ R light without or with sucrose during the 21–27 °C transition. Error bars represent the s.e. (n = three biological replicates), and the centers of the error bars indicate the mean. For (e and f), different letters denote statistically significant differences among the values in the same genotype (one-way ANOVA, Tukey’s HSD, p  <  0.05, n  =  3 biological replicates). g qRT-PCR analysis of the transcript levels of YUC9 and IAA19 in 4-d-old Col-0 and elf3-1 seedlings grown under 50 μmol m⁻² s⁻¹ R light without or with sucrose at either 21 or 27 °C. Asterisks indicate a statistically significant difference based on a two-tailed Student’s t-test (* p  <  0.05, ** p  <  0.01, *** p  <  0.001); n.s. stands for no significant difference. For (f and g), the transcript levels were quantified relative to those of PP2A. Error bars represent the s.e. (n = three biological replicates), and the centers of the error bars indicate the mean. The underlying source data for the hypocotyl measurements in (c), the immunoblots in (d and e), and the qRT-PCR analysis of transcript levels in (f and g) are provided in the Source Data file.