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
Article first published online: 24 MAR 2013
© 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd
The Plant Journal
Volume 74, Issue 4, pages 638–651, May 2013
How to Cite
Maier, A., Schrader, A., Kokkelink, L., Falke, C., Welter, B., Iniesto, E., Rubio, V., Uhrig, J. F., Hülskamp, M. and Hoecker, U. (2013), 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. The Plant Journal, 74: 638–651. doi: 10.1111/tpj.12153
- Issue published online: 11 MAY 2013
- Article first published online: 24 MAR 2013
- Accepted manuscript online: 20 FEB 2013 02:11PM EST
- Manuscript Accepted: 12 FEB 2013
- Manuscript Revised: 7 FEB 2013
- Manuscript Received: 28 DEC 2012
- Deutsche Forschungsgemeinschaft. Grant Numbers: SFB 635-TPC2 to U.H., SFB 635-TPA2 to M.H.
- Bundesministerium für Bildung und Forschung. Grant Number: BIODISC-WIZPLANT to J.U.
- Spanish Ministry of Economy and Competitiveness. Grant Number: MINECO; BIO2010-18820 to V.R.
- protein degradation;
- ubiquitin ligase;
- Arabidopsis thaliana
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.