Phytochrome A elevates plant circadian clock components to suppress shade avoidance in deep canopy shade

Donald P Fraser, Paige E Panter, Ashutosh Sharma, Bhavana Sharma, Antony N Dodd*, Keara A Franklin*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

1 Citation (Scopus)

Abstract

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 (phyB) 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 circadian clock 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, antagonising shade avoidance in deep canopy shade.
Original languageEnglish
Article numbere2108176118
Number of pages9
JournalProceedings of the National Academy of Sciences of the United States of America
Volume118
Issue number27
DOIs
Publication statusPublished - 6 Jul 2021

Bibliographical note

Funding Information:
ACKNOWLEDGMENTS. We thank Elena Monte (Centre for Research in Agricultural Genomics, Barcelona, Spain) for the donation of toc1-101 seed, Stacey Harmer (University of California, Davis, CA) for the donation of rve8-1 seed, Rob McClung (Dartmouth College, Hanover, NH) for prr5-3 and prr7-3 mutants, Takeshi Mizuno for prr5-11/7-11 mutants, and Anthony Hall (Earlham Institute, Norwich, United Kingdom) for the donation of transgenic lines containing CCA1::LUC and TOC1::LUC. This work was funded by Biotechnology and Biological Sciences Research Council (BBSRC) Grants BB/ L01369X, BB/M008711/1, BB/R002045/1, and GEN BB/P013511/1, the Bristol Centre for Agricultural Innovation, and The Leverhulme Trust Grant RPG-2018-216.

Funding Information:
We thank Elena Monte (Centre for Research in Agricultural Genomics, Barcelona, Spain) for the donation of toc1-101 seed, Stacey Harmer (University of California, Davis, CA) for the donation of rve8-1 seed, Rob McClung (Dartmouth College, Hanover, NH) for prr5-3 and prr7-3 mutants, Takeshi Mizuno for prr5-11/7-11 mutants, and Anthony Hall (Earlham Institute, Norwich, United Kingdom) for the donation of transgenic lines containing CCA1::LUC and TOC1::LUC. This work was funded by Biotechnology and Biological Sciences Research Council (BBSRC) Grants BB/ L01369X, BB/M008711/1, BB/R002045/1, and GEN BB/P013511/1, the Bristol Centre for Agricultural Innovation, and The Leverhulme Trust Grant RPG-2018-216.

Publisher Copyright:
© 2021 National Academy of Sciences. All rights reserved.

Keywords

  • Phytochrome A
  • circadian clock
  • deep shade

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