Maier A, Schrader A, Kokkelink L, Falke C, Welter B, Iniesto E, Rubio V, Uhrig JF, Huelskamp M, Hoecker U

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 COP1/SPA ubiquitin ligase since cop1 and spa mutants produce anthocyanins also in darkness. Here, we show that COP1 and SPA proteins interact with the MYB transcription factors ...

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PAP1 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 darkness and this degradation is dependent on the proteasome and 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. At last, 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 transcriptionally as well as posttranslationally. Thus, our findings have identified mechanisms via which the COP1/SPA complex controls anthocyanin levels in Arabidopsis which may be useful for applications in biotechnology directed towards increasing anthocyanin content in plants. © 2013 The Authors. The Plant Journal © 2013 Blackwell Publishing Ltd.

Date: Feb. 20, 2013

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