Shedding (far-red) light on phytochrome mechanisms and responses in land plants.
In order to monitor ambient light conditions, plants rely on functionally diversified photoreceptors. Among these, phytochromes perceive red (R) and far-red (FR) light. FR light does not constitute a photosynthetic energy source; it however influences adaptive and developmental processes. In seed plants, phytochrome A (phyA) acts as FR receptor and mediates FR high irradiance responses (FR-HIRs). It exerts a dual role by promoting e.g. germination and seedling de-etiolation in canopy shade and by antagonising shade avoidance growth. Even though cryptogam plants such as mosses and ferns do not have phyA, they show FR-induced responses. In the present review we discuss the mechanistic basis of phyA-dependent FR-HIRs as well as their dual role in seed plants. We compare FR responses in seed plants and cryptogam plants and conclude on different potential concepts for the detection of canopy shade. Scenarios for the evolution of FR perception and responses are discussed.
Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany.
Anja
A
Possart
Laboratory for Systems and Synthetic Biology, Wageningen University, 6703 HB Wageningen, The Netherlands. Electronic address: christian.fleck@wur.nl.
Christian
C
Fleck
Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany. Electronic address: andreas.hiltbrunner@biologie.uni-freiburg.de.
Andreas
A
Hiltbrunner
D005075:Biological Evolution; D008027:Light; D051942:Phytochrome A / Q000378:metabolism*; D051939:Phytochrome B / Q000378:metabolism*; D010944:Plants / Q000378:metabolism / Q000528:radiation effects*
D051942:Phytochrome A; D051939:Phytochrome B
Arabidopsis; D; Evolution; FR; Far-red high irradiance response; Network response; P(fr); P(r); Physcomitrella patens; Phytochrome; R; Shade avoidance response; dark; far-red light; far-red light absorbing form of phytochromes; red light; red light absorbing form of phytochromes