Harnessing the developmental potential of nucellar cells: barriers and opportunities.

Angiosperm nucellar cells can either use or avoid meiosis in vivo, depending on the developmental context. This unique ability contrasts with the conditions required in vitro, either for a reconstituted oocyte to avoid meiosis and produce clones by somatic cell nuclear transfer (SCNT), or for mammalian stem cells to undergo meiosis and produce synthetic sex cells (gametes). Current biotechnological initiatives to harness the potential of nucellar cells are based on the transfer of apomixis genes to sexual crop plants with the aim of producing clones through seeds. The elusive genetic basis of apomixis compels us to examine whether this process involves epigenetic factors. The elegant and versatile developmental platform available in nucellar cells should be explored as a genome-scale science and compared with mammalian stem cell biology for a holistic understanding of developmental programming and reprogramming in eukaryotes.