Figure 4.

Schematic representation of antagonistic interaction between cytokinin (CK) and abscisic acid (ABA) biosynthesis pathways. CK response element (CKRE) and ABA response element (ABARE) are present in promoter of 9-cis-epoxycarotenoid dioxygenase, a key enzyme of ABA biosynthesis pathway. These response elements may regulate ABA biosynthesis in response to CK and ABA signals. Conversely ABARE present in promoter of Glucosyltransferases, enzymes responsible for CK-conjugation, may modulate CK-conjugation in response to ABA signaling. CK conjugation leads to CK inactivation. Solid lines depict biosynthesis of hormones and responsible enzymes. Dashed lines depict regulation of hormone biosynthesis genes through CRE elements.