Plants are responsive to temperature, and can distinguish differences of 1°C. In A r a b i d o p s i s , warmer temperature accelerates flowering and increases elongation growth (thermomorphogenesis). The mechanisms of temperature perception are however largely unknown. We describe a major thermosensory role for the phytochromes (red light receptors) during the night. Phytochrome null plants display a constitutive warm temperature response, and consistent with this, we show in this background that the warm temperature transcriptome becomes de-repressed at low temperatures. We have discovered phytochrome B (phyB) directly associates with the promoters of key target genes in a temperature dependent manner. The rate of phyB inactivation is proportional to temperature in the dark, enabling phytochromes to function as thermal timers, integrating temperature information over the course of the night.
Plant development is responsive to temperature, and the phenology and distribution of crops and wild plants have already altered in response to climate change.
[...] We used transcriptome analysis to determine whether disrupted thermomorphogenesis in phyABCDE is specific for temperature signaling or is a consequence of misregulated growth pathways.
[...] Since phytochromes are central regulators of plant responses to the environment, their acquisition of a thermally responsive behavior suggests an evolutionary route to integrate temperature information into development. Single amino acid changes as well as post-translational modifications can alter the dark reversion rate, suggesting sequence diversification among phytochromes affords diversity in thermal responsiveness for different climates. The Pfr dark reversion rate represents a sensitive mechanism to integrate small differences in temperature over the night in order to make developmental decisions.
