Interaction of Light and Temperature Signalling in Plants


For plants, light is not only an energy source but also a developmental signal. The colour, intensity, duration and direction of light that a plant receives has a profound effect on its development across all life phases. Mild changes in ambient temperature also have a dramatic effect on plant development, many of which mirror those caused by light. In recent years, it has become apparent that this similarity in phenotypes is due to extensive overlap between components of the light and temperature signalling pathways. This overlap occurs at the level of perception, downstream signalling modules and hormonal response. As a result of this, the photo‐ and thermal responses of plants should always be considered within the context of the prevailing light and temperature conditions.

Key Concepts

  • Light and temperature have similar effects on plant development.
  • Both signalling pathways are tightly integrated at the level of signal perception, signal transduction and hormonal responses.
  • The response to both light and temperature centres on a core set of transcriptional regulators.
  • The activity of some photoreceptors is temperature‐dependent.
  • Light and temperature responses should always be considered in the context of one and other.

Keywords: plant photobiology; plant thermomorphogenesis; plant development; environmental signalling; plant photoreceptors; plant thermosensors

Figure 1. Light and temperature have contrasting effects on hypocotyl elongation. From right to left: representative Arabidopsis seedlings grown for 4 days in darkness at 20 °C (Dark 20), in white light at 20 °C (Light 20), in white light at 20 °C with reduced levels of blue light (Low B 20), in white light at 20 °C with supplementary far‐red light to lower the red to far‐red ratio (+FR 20) or in white light at 28 °C (Light 28).
Figure 2. Representations of the plant photoreceptor families. UVR8 dimer (PDB‐ 4NBM), phot1 dimer (inferred from PDB‐2Z6C & 4HHD), phyB dimer (inferred from PDB‐ 4OUR), cry1 dimer (inferred from PDB‐1U3C) and ztl dimer (inferred from PDB‐5SVG). Chromophores are highlighted in red or blue. UVR8 is activated by UV‐B light (280–315 nm), cryptochromes, phototropins and zeitlupes are activated by UV‐A and B light (390–500 nm) and phytochromes are responsive to R and FR light (600–750 nm). The structures used to produce this figure, and their associated publications can be found at the indicated Protein Data Bank (PDB) identifiers.
Figure 3. Schematic representation of photothermal signalling pathways controlling hypocotyl elongation. Boxes with rounded corners represent proteins and boxes with squared corners represent hormones. Factors that promote hypocotyl elongation are coloured green, and factors that inhibit elongation coloured orange. In darkness, COP1 is active, where it functions to suppress negative regulators of hypocotyl elongation. PIFs and BZR1/BES1 TFs promote hypocotyl elongation by enhancing auxin and brassinosteroid signalling. In the presence of light, UVR8, cryptochromes and phytochromes become active. These photoreceptors inhibit COP1 action, thereby promoting the activity of negative regulators of hypocotyl elongation. HY5/HYH TFs repress auxin signalling and HFR1 forms competitive complexes with the PIFs. ELF3 inhibits PIFs both by repressing PIF expression and by forming competitive complexes. In addition to their effects on COP1, phytochromes also promote ELF3 stability and phytochromes and cryptochromes directly destabilise PIFs and BES1/BRZ1. Low B light deactivates cryptochromes and low R:FR light deactivates phytochromes, reversing these signalling events and leading to hypocotyl elongation through PIFs and BES1/BZR1. Currently, there is strong evidence that warm temperatures promote the reversion of phytochromes to their inactive state and it is theoretically possible that other photoreceptors function in a similar manner. All of the signalling components detailed above have been shown to be involved with both light and temperature signalling in plants, underlining the extraordinary level of interaction between these two signalling pathways.


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Further Reading

Casal JJ and Balasubramanian S (2019) Thermomorphogenesis. Annual Review of Plant Biology 70: 321–346.

Franklin KA and Wigge P (2014) Temperature and Plant Development. Blackwell, Oxford.

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Hayes, Scott(Jan 2020) Interaction of Light and Temperature Signalling in Plants. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0027978]