CYP707A

CYP707A is a subfamily of plant cytochrome P450 enzymes that function as ABA 8'-hydroxylases, catalyzing the rate-limiting step in abscisic acid (ABA) catabolism. The enzymatic reaction adds a hydroxyl group at the 8'-position of ABA to form 8'-hydroxy ABA, which non-enzymatically rearranges and is further oxidized to ABA catabolites such as phaseic acid and dihydrophaseic acid, thereby reducing cellular ABA levels. This pathway helps regulate ABA signaling during development and in response to environmental stress.

In Arabidopsis thaliana, the CYP707A gene family comprises four members—CYP707A1, CYP707A2, CYP707A3, and CYP707A4. All encode endoplasmic reticulum–localized P450 monooxygenases with tissue- and development-specific expression patterns. Their expression is influenced by ABA and abiotic stresses such as drought, salt, and cold, contributing to feedback control of ABA homeostasis. Functional studies show that altering CYP707A activity changes ABA content and associated phenotypes including seed dormancy, germination, stomatal conductance, and stress responsiveness. For example, loss-of-function mutants tend to accumulate ABA and exhibit altered dormancy and stress responses, whereas increased CYP707A activity promotes ABA breakdown and can diminish these ABA-dependent traits.

Across land plants, CYP707A homologs are widespread, reflecting a conserved role in ABA catabolism and hormone homeostasis that interacts with other hormonal and environmental signaling pathways. The family remains a focus of research for improving crop drought responses and seed biology.

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