Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 118, Issue 27, Pages -Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.2108176118
Keywords
phytochrome A; shade avoidance; circadian clock
Categories
Funding
- Biotechnology and Biological Sciences Research Council (BBSRC) [BB/L01369X, BB/M008711/1, BB/R002045/1, GEN BB/P013511/1]
- Bristol Centre for Agricultural Innovation
- Leverhulme Trust [RPG-2018-216]
- BBSRC [BB/R002045/1, BB/M008711/1] Funding Source: UKRI
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Shade-avoiding plants can adjust their responses based on the presence of neighboring vegetation. This response is regulated by the phytochrome B photoreceptor, which becomes inactive in environments with low red to far-red light ratios. In deep canopy shade, plants can suppress stem elongation to counteract shade avoidance and promote survival.
Shade-avoiding plants can detect the presence of neighboring vegetation and evoke escape responses before canopy cover limits photosynthesis. Rapid stem elongation facilitates light foraging and enables plants to overtop competitors. A major regulator of this response is the phytochrome B photoreceptor, which becomes inactivated in light environments with a low ratio of red to far-red light (low R:FR), characteristic of vegetational shade. Although shade avoidance can provide plants with a competitive advantage in fast-growing stands, excessive stem elongation can be detrimental to plant survival. As such, plants have evolved multiple feedback mechanisms to attenuate shade-avoidance signaling. The very low R:FR and reduced levels of photosynthetically active radiation (PAR) present in deep canopy shade can, together, trigger phytochrome A (phyA) signaling, inhibiting shade avoidance and promoting plant survival when resources are severely limited. The molecular mechanisms underlying this response have not been fully elucidated. Here, we show that Arabidopsis thaliana phyA elevates early-evening expression of the central circadianclock components TIMING OF CAB EXPRESSION 1 (TOC1), PSEUDO RESPONSE REGULATOR 7 (PRR7), EARLY FLOWERING 3 (ELF3), and ELF4 in photocycles of low R:FR and low PAR. These collectively suppress stem elongation, antagonizing shade avoidance in deep canopy shade.
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