Figure 5.

PIN-mediated auxin transport and distribution during Arabidopsis embryo development. The upper panel illustrates embryo development, auxin transport and distribution from the one-cell stage to the triangular-stage. PIN7 become expressed from the earliest stages of embryo development (marked by yellow arrow), later also PIN1 and PIN4 become present (marked by red and blue arrows, respectively). Notice that during embryo development the polarity of PIN localization changes. PIN expression correlates with the accumulation of auxin (highlighted in green) first in the apical cell and developing proembryo, and later at the basal part of the embryo with a maximum in the upper suspensor cell. The lower panel shows pictures of auxin accumulation as indirectly visualized by DR5rev::GFP. Images adapted from Friml et al (2003b) and Benkova et al (2003).