CONSTITUTIVELY PHOTOMORPHOGENIC1 is required for the UV-B response in Arabidopsis.
CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) is a negative regulator of photomorphogenesis in Arabidopsis thaliana. COP1 functions as an E3 ubiquitin ligase, targeting select proteins for proteasomal degradation in plants as well as in mammals. Among its substrates is the basic domain/leucine zipper (bZIP) transcription factor ELONGATED HYPOCOTYL5 (HY5), one of the key regulators of photomorphogenesis under all light qualities, including UV-B responses required for tolerance to this environmental threat. Here, we report that, in contrast with the situation in visible light, COP1 is a critical positive regulator of responses to low levels of UV-B. We show that in the cop1-4 mutant, flavonoid accumulation and genome-wide expression changes in response to UV-B are blocked to a large extent. COP1 is required for HY5 gene activation, and both COP1 and HY5 proteins accumulate in the nucleus under supplementary UV-B. SUPPRESSOR OF PHYTOCHROME A-105 family proteins (SPA1 to SPA4) that are required for COP1 function in dark and visible light are not essential in the response to UV-B. We conclude that COP1 performs a specific and novel role in the plants' photomorphogenic response to UV-B, coordinating HY5-dependent and -independent pathways, which eventually results in UV-B tolerance.
Oravecz
Attila
A
Institute of Biology II/Botany, University of Freiburg, D-79104 Freiburg, Germany.
Baumann
Alexander
A
Máté
Zoltán
Z
Brzezinska
Agnieszka
A
Molinier
Jean
J
Oakeley
Edward J
EJ
Adám
Eva
E
Schäfer
Eberhard
E
Nagy
Ferenc
F
Ulm
Roman
R
D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D005419:Flavonoids / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D017343:Genes, Plant; D018546:Hypocotyl / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism; D015533:Transcriptional Activation; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014466:Ultraviolet Rays
D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D005419:Flavonoids; C109254:HY5 protein, Arabidopsis; D009687:Nuclear Proteins; C471983:AT2G32950 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases