Abstract
Multicellular organisms efficiently use symmetric cell division and asymmetric cell division, and control the number and the type of cells. In protonemata of Physcomitrella patens, they normally grow by asymmetric cell division and elongation of the apical cells. When treated with abscisic acid (ABA), protonemata divide symmetrically to produce numerous spherical cells, called brood cells. It is largely unknown how ABA regulates such alternation of cell division mode and change of cell fate.
We transiently over-expressed about 3000 full-length cDNAs in protoplasts, and identified three genes which induced brood cell-like cells. One of them encoded ABI3/VP1 orthologue, a positive regulator of ABA signaling pathway, and the other two were presumed to encode a proline-rich cell wall protein and a glycosyltransferase, respectively. Conditionally over-expressed these two genes induced rounded, brood cell-like cells, in which a degree of the angle of the septa was disarranged, indicating that cell polarity was destroyed and that these two genes were in fact involved in ABA responses. Further functional analyses to study knock-out phenotype and protein localization are under progress.
