title: Light and the E3 ubiquitin ligase COP1/SPA control the protein stability of the MYB transcription factors PAP1 and PAP2 involved in anthocyanin accumulation in Arabidopsis.
abstract: Anthocyanins are natural pigments that accumulate only in light-grown and not in dark-grown Arabidopsis plants. Repression of anthocyanin accumulation in darkness requires the CONSTITUTIVELY PHOTOMORPHOGENIC1/SUPPRESSOR OF PHYA-105 (COP1/SPA) ubiquitin ligase, as cop1 and spa mutants produce anthocyanins also in the dark. Here, we show that COP1 and SPA proteins interact with the myeloblastosis (MYB) transcription factors PRODUCTION OF ANTHOCYANIN PIGMENT1 (PAP)1 and PAP2, two members of a small protein family that is required for anthocyanin accumulation and for the expression of structural genes in the anthocyanin biosynthesis pathway. The increased anthocyanin levels in cop1 mutants requires the PAP1 gene family, indicating that COP1 functions upstream of the PAP1 gene family. PAP1 and PAP2 proteins are degraded in the dark and this degradation is dependent on the proteasome and on COP1. Hence, the light requirement for anthocyanin biosynthesis results, at least in part, from the light-mediated stabilization of PAP1 and PAP2. Consistent with this conclusion, moderate overexpression of PAP1 leads to an increase in anthocyanin levels only in the light and not in darkness. Here we show that SPA genes are also required for reducing PAP1 and PAP2 transcript levels in dark-grown seedlings. Taken together, these results indicate that the COP1/SPA complex affects PAP1 and PAP2 both transcriptionally and post-translationally. Thus, our findings have identified mechanisms via which the COP1/SPA complex controls anthocyanin levels in Arabidopsis that may be useful for applications in biotechnology directed towards increasing anthocyanin content in plants.
authors: Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, BioCenter, Zülpicher Str. 47b, 50674, Cologne, Germany.
authors: Alexander
authors: A
authors: Maier
authors: Andrea
authors: A
authors: Schrader
authors: Leonie
authors: L
authors: Kokkelink
authors: Christian
authors: C
authors: Falke
authors: Bastian
authors: B
authors: Welter
authors: Elisa
authors: E
authors: Iniesto
authors: Vicente
authors: V
authors: Rubio
authors: Joachim F
authors: JF
authors: Uhrig
authors: Martin
authors: M
authors: Hülskamp
authors: Ute
authors: U
authors: Hoecker
mesh_terms: D000872:Anthocyanins / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003624:Darkness; D015536:Down-Regulation; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D008027:Light; D046912:Multiprotein Complexes; D009154:Mutation; D000073718:Pancreatitis-Associated Proteins; D030821:Plants, Genetically Modified; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D059748:Proteolysis; D011993:Recombinant Fusion Proteins; D036226:Seedlings / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
chemical_list: D000872:Anthocyanins; D029681:Arabidopsis Proteins; D046912:Multiprotein Complexes; D000073718:Pancreatitis-Associated Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D044767:Ubiquitin-Protein Ligases; C502612:AT1G56650 protein, Arabidopsis; C514560:PAP2 protein, Arabidopsis; C000612141:REG3A protein, human; C471983:AT2G32950 protein, Arabidopsis