Chromatin assembly factor 1 regulates the cell cycle but not cell fate during male gametogenesis in Arabidopsis thaliana.

The interdependence of cell cycle control, chromatin remodeling and cell fate determination remains unclear in flowering plants. Pollen development provides an interesting model, as it comprises only two cell types produced by two sequential cell divisions. The first division separates the vegetative cell from the generative cell. The generative cell divides and produces the two sperm cells, transported to the female gametes by the pollen tube produced by the vegetative cell. We show in Arabidopsis thaliana that loss of activity of the Chromatin assembly factor 1 (CAF1) pathway causes delay and arrest of the cell cycle during pollen development. Prevention of the second pollen mitosis generates a fraction of CAF1-deficient pollen grains comprising a vegetative cell and a single sperm cell, which both express correctly cell fate markers. The single sperm is functional and fertilizes indiscriminately either female gamete. Our results thus suggest that pollen cell fate is independent from cell cycle regulation.