Abstract
Genome integrity is continuously threatened by external stress or by errors in DNA replication, thus a response to DNA damage is essential for survival and continuous growth of plants. To prevent DNA-damaged cells from proliferating, plants provoke the DNA damage checkpoint, but its regulatory mechanisms remain unknown.
Recently, we found that DNA double-strand breaks (DSBs) trigger transition to endocycle, leading to endoreduplication, in Arabidopsis. In plants, exit from mitotic cell cycle is often associated with endocycle, in which cell increases their DNA content by repeating DNA replication without mitosis. We also found that the protein degradation of CDKB2 was enhanced in response to DSBs. This result suggests that CDKB2 degradation may be involved in switching from the mitotic cell cycle to the endocycle in response to DSBs.
To verify this hypothesis, we are identifying cis regulatory motifs important for DSB-induced CDKB2 degradation. For this purpose, we generated plants expressing several truncated versions of CDKB2 or CDKB2 with several combinations of amino acid substitutions, which are fused with GUS reporter gene, and found some possible important elements.
