The ABF-MAX3/4 regulatory nodes repress Arabidopsis shoot branching under drought

Shoot branching is a key determinant of plant architecture and yield, and reduced shoot branching may enhance plant survival and promote effective seed maturation under drought stress. However, it remains unknown how plants alter shoot branching under drought. Here, we found that drought stress represses shoot branching in Arabidopsis. Abscisic acid (ABA)-responsive element-binding transcription factors (ABFs), central regulators of osmotic stress responses, transcriptionally activate the strigolactone (SL) biosynthesis genes MORE AXILLARY GROWTH 3 and 4 (MAX3/4), thereby inhibiting branching. The loss-of-function abf octuple mutant impairs MAX gene induction and branching repression under osmotic stress or ABA treatment, a defect that can be rescued by the SL analog GR-24. Our findings reveal a molecular pathway through which ABFs respond to drought stress signals to limit shoot branching by activating MAX3/4 expression, underscoring their central role in adapting plant architecture to adverse conditions.