Figure 8.

Proposed model for auxin (from the ovary and from the apical shoot)-GA interaction on parthenocarpic fruit-set. Auxin accumulated in unpollinated ovary upon NPA application and auxin transported from the apical shoot (without entering in the ovary) regulate GA metabolism genes in the ovary in opposite ways, associated with induction (auxin in the ovary) and repression (auxin from the apical shoot) of fruit-set. For clarity, only GA20ox1, the main GA20ox gene regulated in both cases, is given in the scheme. GA20ox2, GA3ox1, and GA3ox2 transcript levels also increased in NPA-induced ovaries at day 10 after treatment but not in decapitated plants. The question mark (?) means that IAA from the apex does not need to enter the ovary for fruit-set inhibition and that this effect depends on unknown second messenger(s). GGPP, Geranylgeranyl diphosphate.