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Quantitative Genetics

continuation of GWAS projects


Topoisomerase VI - TOPOVI

TOPOVI components are required for normal levels of endoreduplication, chromatin condensation and silencing in A. thaliana. Results point to an activated ATM/ATR-dependent DNA damage repair and endoreduplication affecting checkpoint. (see work on MIDGET, one of the TOPOVI components)

TOPOVI mutants are defective in COP1-dependent phenotypes. Being identified as an interactor of COP1, we found that MIDGET links light signalling and endoreduplication. MIDGET does not show characteristics of a COP1 target – in contrast, it influences COP1 nuclear localization. Genetic interactions were found in respect to flowering time with COP1 and SPA1 mutants.


Kirik V, Schrader A, Uhrig JF, Hulskamp M (2007) MIDGET unravels functions of the Arabidopsis topoisomerase VI complex in DNA endoreduplication, chromatin condensation, and transcriptional silencing. Plant Cell 19: 3100-3110

Schrader A, Welter B, Hulskamp M, Hoecker U, Uhrig JF (2013) MIDGET connects COP1-dependent development with endoreduplication in Arabidopsis thaliana. Plant J 75: 67-79

Schrader A, Uhrig J (2013) MIDGET cooperates with COP1 and SPA1 to repress flowering in Arabidopsis thaliana. Plant Signal Behav 8



Anthocyanidin accumulation is one of the COP1-dependent phenotypes. PAP2, a transcriptional activator of anthocyanidin biosynthesis, was found to interact with COP1. Competing for a target binding site in COP1, PAP2 was classified a putative target. Indeed, its stability is dependent on COP1.


Results from this project have been published with the Hoecker lab:

Maier A, Schrader A, Kokkelink L, Falke C, Welter B, Iniesto E, Rubio V, Uhrig JF, Hulskamp M, 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. Plant J 74: 638-651