ArabidopsisSHORT HYPOCOTYL UNDER BLUE1 Contains SPX and EXS Domains and Acts in Cryptochrome Signaling
Open Access
- 24 February 2006
- journal article
- Published by Oxford University Press (OUP) in Plant Cell
- Vol. 18 (4), 921-934
- https://doi.org/10.1105/tpc.105.037879
Abstract
Photomorphogenesis is regulated by red/far-red light–absorbing phytochromes and blue/UV-A light–absorbing cryptochromes. We isolated an Arabidopsis thaliana blue light mutant, short hypocotyl under blue1 (shb1), a knockout allele. However, shb1-D, a dominant allele, exhibited a long-hypocotyl phenotype under red, far-red, and blue light. The phenotype conferred by shb1-D was caused by overaccumulation of SHB1 transcript and recapitulated by overexpression of SHB1 in Arabidopsis. Therefore, SHB1 acts in cryptochrome signaling but overexpression may expand its signaling activity to red and far-red light. Consistent with this, overexpression of SHB1 enhanced the expression of PHYTOCHROME-INTERACTING FACTOR4 (PIF4) under red light. PIF4 appears to specifically mediate SHB1 regulation of hypocotyl elongation and CHLOROPHYLL a/b BINDING PROTEIN3 or CHALCONE SYNTHASE expression under red light. Overexpression of SHB1 also promoted proteasome-mediated degradation of phytochrome A and hypocotyl elongation under far-red light. Under blue light, shb1 suppressed LONG HYPOCOTYL IN FAR-RED LIGHT1 (HFR1) expression and showed several deetiolation phenotypes similar to hfr1-201. However, the hypocotyl and cotyledon-opening phenotypes of shb1 were opposite to those of hfr1-201, and HFR1 acts downstream of SHB1. SHB1 encodes a nuclear and cytosolic protein that has motifs homologous with SYG1 protein family members. Therefore, our studies reveal a signaling step in regulating cryptochrome- and possibly phytochrome-mediated light responses.Keywords
This publication has 56 references indexed in Scilit:
- Phytochrome-Specific Type 5 Phosphatase Controls Light Signal Flux by Enhancing Phytochrome Stability and Affinity for a Signal TransducerCell, 2005
- Structure and Expression Profile of the Arabidopsis PHO1 Gene Family Indicates a Broad Role in Inorganic Phosphate HomeostasisPlant Physiology, 2004
- Blue Light-Dependent in Vivo and in Vitro Phosphorylation of Arabidopsis Cryptochrome 1Plant Cell, 2003
- Cryptochromes: Enabling Plants and Animals to Determine Circadian TimeCell, 2003
- Novel ATP-binding and autophosphorylation activity associated with Arabidopsis and human cryptochrome-1European Journal of Biochemistry, 2003
- TheArabidopsis SRR1gene mediates phyB signaling and is required for normal circadian clock functionGenes & Development, 2003
- A Phytochrome-Associated Protein Phosphatase 2A Modulates Light Signals in Flowering Time Control in ArabidopsisPlant Cell, 2002
- Identification and Characterization of the Arabidopsis PHO1 Gene Involved in Phosphate Loading to the XylemPlant Cell, 2002
- Interaction of the Response Regulator ARR4 with Phytochrome B in Modulating Red Light SignalingScience, 2001
- Aux/IAA Proteins Are Phosphorylated by Phytochrome in VitroPlant Physiology, 2000