Abstract
The moss Physcomitrella patens development starts from a germinating spore that gives rise to a filamentous structure called protonema. Bud that is arisen form protonema develops to give rise to a leafy shoot called gametohpore. After excision of a leaf from a gametophore, leaf cells facing to the dissected cells change to protonemal cells, associated with cell cycle reactivation. To explore molecular framework governing the cell fate change from leaf cells to protonemal cells and the cell cycle reactivation in excised leaf, we have focused on the E2F transcription factors, which control the G1/S phase transition of the cell cycle in other species. We identified four genes encoding typical E2F transcription factors (E2F;1 to E2F;4) in P. patens genome and isolated gain-of-function mutants of E2Fs. One of the mutants produced ectopic lobed brade on leaf of gametophore. Furthermore, when the leaf was excised from the gametophore, the leaf cells in the top of the lobed brade produced protonemal cell. On the basis of these results, we will discuss how E2Fs control both cell cycle and cell fate determination.
