Fig. 1: Dissecting phyB-dependent and phyB-independent thermosensing in the light.

a Temperature-response curves of hypocotyl elongation under various intensities of R light reveal distinct thermosensing mechanisms in the light: a mechanism depending solely on phyB thermal reversion (phyB dependent) at low temperatures and a mechanism also requiring thermosensing independently of phyB thermal reversion (multisensor dependent) at high temperatures. Hypocotyl lengths were measured in 4-d-old Col-0 seedlings grown at 12 °C, 16 °C, 21 °C, and 27°C under a range of continuous R light intensities from 0.1 to 50 μmol m⁻² s⁻¹. The blue and pink shades highlight the temperature responses at the low-temperature range between 12 and 21 °C (solid lines) and the high-temperature range between 21 and 27 °C (dashed lines), respectively. b Distinct effects of light intensity on the low- and high-temperature responses. The phyB-dependent low-temperature (12–21 °C) and multisensor-dependent high-temperature (21–27 °C) responses were quantified as the percent increase in hypocotyl length in the respective temperature ranges and plotted against light intensity. c YHB^g seedlings lack the phyB-dependent low-temperature response. The left panel shows the temperature-response curve of 4-d-old Ler and YHB^g seedlings grown under 2.5 μmol m⁻² s⁻¹ R light. The blue shade highlights the phyB-dependent response between 12 and 21 °C. The right panel shows the hypocotyl lengths of Ler and YHB^g seedlings at 12 and 21 °C. The blue bars show the relative response, which is defined as the hypocotyl response at 21 °C in YHB^g relative to that in Ler (set at 100%). d Images of 4-d-old Ler and YHB^g seedlings grown under 50 μmol m⁻² s⁻¹ R light at either 21 or 27 °C. e YHB^g seedlings retained the multisensor-dependent high-temperature response. The left panel shows the temperature-response curve of 4-d-old Ler and YHB^g seedlings grown under 50 μmol m⁻² s⁻¹ R light. The pink shade highlights the multisensor-dependent response between 21 and 27 °C. The right panel shows the hypocotyl lengths of Ler and YHB^g seedlings at 21 and 27 °C. The magenta bars show the relative response, which is defined as the hypocotyl response at 27 °C in YHB^g relative to that in Ler (set at 100%). For (a–c and e), the error bars represent the s.e. (n = three biological replicates), and the centers of the error bars indicate the mean. For (c and e), a significant difference in the relative response between Ler and YHB^g was defined as a greater than twofold and statistically significant change (p < 0.05) in the temperature response based on a two-tailed Student’s t-test (**** indicates p < 0.0001) and otherwise was defined as no significant difference (n.s). The underlying source data for the hypocotyl measurements in (a–c and e) are provided in the Source Data file.