Abstract
A stem cell is undifferentiated, self-renews, and also gives rise to a cell to be differentiated. Formation of several types of stem cells to produce different types of differentiated cells is properly regulated during development of multicellular organisms. However, molecular mechanisms for the stem cell characterization have been largely unknown.
Here we show that AINTEGUMENTA/PLETHORA/BABY BOOM (APB) orthologs PpAPBs (PpAPB1,2,3 and 4 are involved in the stem cell characterization in the moss Physcomitrella patens. Gametophore stem cells were induced by exogenous cytokinin in the wild type, while the quadruple disruptants did not form any gametophore stem cells with exogenous cytokinin application. These results suggest that the PpAPBs play a critical role in characterization of a gametophore stem cell. Meanwhile, the expression of PpAPBs is regulated by not cytokinin but auxin. We will discuss the roles of PpAPBs, auxin, and cytokinin in stem cell characterization.
