Photoreceptor signaling networks in plant responses to shade.
The dynamic light environment of vegetation canopies is perceived by phytochromes, cryptochromes, phototropins, and UV RESISTANCE LOCUS 8 (UVR8). These receptors control avoidance responses to preclude exposure to limiting or excessive light and acclimation responses to cope with conditions that cannot be avoided. The low red/far-red ratios of shade light reduce phytochrome B activity, which allows PHYTOCHROME INTERACTING FACTORS (PIFs) to directly activate the transcription of auxin-synthesis genes, leading to shade-avoidance responses. Direct PIF interaction with DELLA proteins links gibberellin and brassinosteroid signaling to shade avoidance. Shade avoidance also requires CONSTITUTIVE PHOTOMORPHOGENESIS 1 (COP1), a target of cryptochromes, phytochromes, and UVR8. Multiple regulatory loops and the input of the circadian clock create a complex network able to respond even to subtle threats of competition with neighbors while still compensating for major environmental fluctuations such as the day-night cycles.
IFEVA, Facultad de Agronomía, Universidad de Buenos Aires and CONICET, 1417 Buenos Aires, Argentina. casal@ifeva.edu.ar
Jorge J
JJ
Casal
D017753:Ecosystem; D005875:Gibberellins / Q000378:metabolism; D008027:Light; D055519:Photoreceptors, Plant / Q000378:metabolism*; D010834:Phytochrome / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism; D010944:Plants / Q000378:metabolism*; D015398:Signal Transduction
D005875:Gibberellins; D055519:Photoreceptors, Plant; D010937:Plant Growth Regulators; D010834:Phytochrome