Mechanisms of cell specification
We are interested in the intra- and intercellular mechanisms underlying the specification of the distinct cell types. To identify factors necessary for the regulation of egg cell fate, we have screened for mutants with deviating egg cell marker gene expression. The first class of mutants identified includes the lachesis (lis), clotho (clo) and atropos (ato) mutants. All three mutants are characterized by the formation of super-numerary egg cells (Fig. 1), which differentiate at the expense of the adjacent synergids and central cell. Additionally, antipodals of mutant gametophytes can adopt a central cell fate. Our data show that all cells in the female gametophyte can differentiate into gametes, and that this gametic competence is repressed by LIS, CLO and ATO (Groß-Hardt et al., 2007, Moll et al., 2008).