Figure 5. Role of RBR1 during the Arabidopsis life cycle.

Fully developed embryos present in the seeds grow after germination to produce young seedlings containing cotyledons as well as root and shoot apical meristems responsible for the growth of the root system and the aerial part, respectively. Rosette leaves appear later during vegetative growth. After the transition to the reproductive stage, flowers are produced where some cells specialize into precursors of germinal cells that produce haploid cells after meiosis. These haploid cells divide 2 or 3 times to produce the male and female gametophytes (mature pollen and embryo sac), respectively. After double fertilization, an embryo and the surrounding endosperm are formed inside the seed. Green and violet arrows denote the sporophytic and gametophytic phases, respectively. Most of these developmental stages and transitions are affected by RBR1 (see the text for details).