Genes normally expressed in the endosperm are expressed at early stages ofmicrospore embryogenesis in maize

Reproduction in flowering plants is characterized by double fertilization a nd the resulting formation of both the zygotic embryo and the associated en dosperm. In many species it is possible to experimentally deviate pollen de velopment towards an embryogenic pathway. This developmental switch, referr ed to as microspore embryogenesis or androgenesis, leads to the formation o f embryos similar to zygotic embryos. In a screen for genes specifically ex pressed during early androgenesis, two maize genes were isolated by mRNA di fferential display. Both genes represent new molecular markers expressed at a very young stage of androgenic embryogenesis. When their expression patt ern was studied during normal reproductive development, both showed early e ndosperm-specific expression. Investigation of the cytological features of young androgenic embryos revealed that they present a partially coenocytic organization similar to that of early endosperm. These findings suggest tha t maize androgenesis may possibly involve both embryogenesis and the establ ishment of endosperm-like components.