Figure 1.

Tentative model highlighting the relevant components contributing to the acquisition of embryogenic competence. Inductive signals trigger responses increasing the level of endogenous auxin, which promotes the expression of SE marker genes such as WUS, SERK and BBM. Auxin also induces Pgbs, which, through suppression of NO, initiate a cascade of events mediated by JA and MYC2 and culminating with changes in auxin level and localization. The process also requires oxidative responses. Genes indicated in the figure are described in more detail in the text.