Document Detail

Genetic and transgenic evidence that phytochromes A and B act to modulate the gravitropic orientation of Arabidopsis thaliana hypocotyls.
MedLine Citation:
PMID:  11536725     Owner:  NASA     Status:  MEDLINE    
Hypocotyls of Arabidopsis thaliana exhibit negative gravitropism in the dark, growing against the gravity vector. The direction of growth is randomized in red light (R). In single mutants lacking either phytochrome A or B randomization of hypocotyl orientation in R is retained. However, a double mutant lacks this response, indicating that either phytochrome A or B is capable of inducing randomization and phytochrome A and B are the only phytochromes involved in this process. The induction of randomization was confirmed using lines that express to different levels PHYA and PHYB cDNAs. Overexpression of PHYA cDNAs induced randomization of hypocotyl orientation in the dark. Dark randomization was also seen in the phyB-1 mutant but not in two other phyB alleles, suggesting that dark randomization in the phyB-1 line may be due to a second mutation. When germination was induced by gibberellin, rather than exposure to brief white light, randomization in the dark associated with phytochrome A overproduction was not observed but was retained in the phyB-1 mutant. Overexpression of PHYB cDNAs induced a light-dependent randomization of hypocotyl orientation that responded to R:far-red light ratio. We conclude that the default situation in Arabidopsis hypocotyls is, therefore, negative gravitropism, and either phytochrome A or phytochrome B can mediate randomization.
P R Robson; H Smith
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Plant physiology     Volume:  110     ISSN:  0032-0889     ISO Abbreviation:  Plant Physiol.     Publication Date:  1996 Jan 
Date Detail:
Created Date:  1998-02-22     Completed Date:  1998-02-22     Revised Date:  2010-09-14    
Medline Journal Info:
Nlm Unique ID:  0401224     Medline TA:  Plant Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  211-6     Citation Subset:  S    
Department of Botany, University of Leicester, United Kingdom.
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MeSH Terms
Arabidopsis / genetics*,  growth & development,  physiology,  radiation effects
Arabidopsis Proteins
DNA, Complementary
DNA, Plant
Gene Expression Regulation, Plant
Gravitropism / genetics,  physiology*,  radiation effects
Hypocotyl / genetics*,  growth & development,  physiology,  radiation effects
Photoreceptor Cells*
Phytochrome / genetics*,  physiology
Phytochrome A
Phytochrome B
Plants, Genetically Modified
Transcription Factors*
Reg. No./Substance:
0/Arabidopsis Proteins; 0/DNA, Complementary; 0/DNA, Plant; 0/PHYA protein, Arabidopsis; 0/PHYB protein, Arabidopsis; 0/Phytochrome A; 0/Transcription Factors; 11121-56-5/Phytochrome; 136250-22-1/Phytochrome B

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