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Phytochrome interacting factors 4 and 5 redundantly limit seedling de‐etiolation in continuous far‐red light
Author(s) -
Lorrain Séverine,
Trevisan Martine,
Pradervand Sylvain,
Fankhauser Christian
Publication year - 2009
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2009.03971.x
Subject(s) - phytochrome , etiolation , phytochrome a , hypocotyl , shade avoidance , seedling , far red , biology , photomorphogenesis , mutant , transcription factor , microbiology and biotechnology , genetics , arabidopsis , botany , gene , red light , biochemistry , enzyme
Summary Phytochromes are red/far‐red photosensors that regulate numerous developmental programs in plants. Among them, phytochrome A (phyA) is essential to enable seedling de‐etiolation under continuous far‐red (FR) light, a condition that mimics the environment under a dense canopy. The ecological relevance of this response is demonstrated by the high mortality rate of phyA mutant plants that germinate in deep vegetational shade. phyA signaling involves direct interaction of the photoreceptor with phytochrome‐interacting factors PIF1 and PIF3, members of the bHLH transcription factor family. Here we investigated the involvement of PIF4 and PIF5 in phyA signaling, and found that they redundantly control de‐etiolation in FR light. The pif4 pif5 double mutant is hypersensitive to low fluence rates of FR light. This phenotype is dependent on FR light perception by phyA, but does not rely on alterations in the phyA level. Our microarray analysis shows that PIF4 and PIF5 are part of an inhibitory mechanism that represses the expression of some light‐responsive genes in the dark, and that they are also needed for full expression of several growth‐related genes in the light. Unlike PIF1 and PIF3, PIF4 and PIF5 are not degraded in response to FR light, indicating that they are light‐regulated by a different mechanism. Our genetic analysis suggests that this is achieved through sequestration of these PIFs by the closely related bHLH transcription factor HFR1 (long hypocotyl in FR light).