Positional signals establishment in the regulation of female germline specification

The female germline specification process of a single megaspore mother cell (MMC) of ovule primordium (nucellus) is intriguingly complex because it involves the interaction of different pathways tightly linked with positional information. Various Arabidopsis genes, including the stem cell promoting factor WUSCHEL, have already been shown to be involved in this precise regulation process. Recently, there have been some reviews on MMC specialization, mainly from the aspects of epigenetics, microRNAs and gene regulatory networks. However, those reviews have not taken into consideration the function of positional signals in female germline specification. Here, we review the major progress in the cell fate control of female germline specification, highlighting the functions of positional cues.