Abstract
Regulation of plant cell cycle shares highly similarity with the system controlling in mammals, in which the signal pathway mediated through Rb (retinoblastoma) plays important roles in regulation of the G1/S transition. A previous study reported that AtRBR1, encoding the only Arabidopsis Rb, is related to the stem cell maintenance of the root. However, it remains to be elucidated that AtRBR1 function concerns the phosphorylation status of AtRBR1 protein in plants.
In this study, we analyzed this issue by using Arabidopsis suspension cultured MM2d cells. When MM2d cells are subjected to re-entry into cell cycle, hyper-phospholylated AtRBR1 protein increases during G1/S phase. Additionally, pull-down assay revealed that hypo-phospholylated AtRBR1 binds to E2F, but hyper-phospholylated AtRBR1 is unable to bind. These results suggest that, like mammalian Rb, phosphorylation probably results in inactivation of AtRBR1 and the subsequent release of active E2F/DP transcription factors, thereby progressing the cell cycle to S phase.
