A Model for DA1, DAR1, and DAR2 Function in Endoreduplication.
In the wild type, DA1, DAR1, and DAR2 act redundantly to regulate endoreduplication by modulating the stability of the transcription factors TCP14/15. TCP14/15 repress endoreduplication by directly regulating the expression of several cell-cycle genes (e.g., RBR and CYCA3;2). Other factors might also mediate the effects of DA1, DAR1, and DAR2 on endoreduplication. In da1-ko1 dar1-1 dar2-1, the transcription factors TCP14/15 are accumulated, resulting in increased expression of RBR and CYCA2;3 and strong repression of endoreduplication.