Stem Cell Maintenance in the Shoot Apical Meristems and during Axillary Meristem Development

In plants, the shoot apical meristem (SAM), which is formed during embryogenesis, plays a crucial role in postembryonic development of the above-ground shoots. The SAM harbors pluripotent stem cells, which provide daughter cells to differentiate lateral organs and stems. As the plant grows, the primary shoot generates the axillary meristems, which are responsible for secondary shoot development. During the development of axillary meristem, stem cells must be established and maintained to build up the axillary meristems. While the mechanism underlying stem cell maintenance in the SAM, including the WUSCHEL-CLAVATA negative feedback loop, has been well elucidated, studies on the regulation of stem cell maintenance during axillary meristem development have only just begun. In this minireview, we describe the genetic mechanisms underlying stem cell maintenance in both the established SAM and the developing axillary meristem in two model plants, Arabidopsis thaliana and Oryza saliva (rice). We also discuss the function of genes that are specific or shared between the established and developing meristems or between Arabidopsis and rice.