Sexual development in the pea is presaged by altered expression of arabinogalactan protein

Abstract

FLOWERS contain the reproductive cells of angiosperms. Floral meristems develop apically or subapically from vegetative axes, and the flower itself is often regarded as homologous with a compressed and determinate shoot¹. Although in many extant angiosperms the fertile floral organs (stamens and carpels) resemble leaves in both development and morphology², the struc-tures that give rise to the germ cells inside them (the anther and ovule) have no counterpart in any vegetative organ. The reproduc-tive cells of angiosperms therefore develop after a period of exclusively vegetative growth and, in contrast to those of animals, have no direct antecedents in the embryo³. So far, the molecular mechanisms that set the reproductive cells apart from those of the other components of the flower or from the vegetative organs are unknown. Here we describe an early and specific developmental switch in stamen and carpel primordia of pea (Pisum sativum L.) which alters expression of a plasma membrane arabinogalactan protein⁴ epitope in the progenitors of the germ cells, and which subsequently affects the gametes, zygote and globular-stage embryo.