Abstract
Plastids and mitochondria have their own genomes descended from their ancestors, and the organelle DNA replications (ODR) of plant cells are coordinated with the nuclear DNA replication (NDR) as ODR precedes NDR during a cell cycle progression. Recently, we identified that a tetrapyrrole compound, Mg-Protoporphyrin IX (Mg-ProtoIX), is a cell-cycle coordinator from organelle to NDR in plant cells. Mg-ProtoIX somehow activates CDKA to direct the G1/S transition1. However, the molecular mechanism for CDKA activation remained elusive. Here we identified an F-box protein Fbx3, which inhibits CDKA by ubiquitinating the cyclin 1 and inducing the degradation. Mg-ProtoIX binds to Fbx3 and inhibits the cyclin 1 ubiquitination. We will provide a model of molecular mechanisms for coordination among organelles and nuclear DNA replication.
1 Kobayashi, Y. et al. Proc. Natl. Acad. Sci. USA 106, 803 (2009).
