Hydrolysis of abscisic acid glucose ester occurs locally and quickly in response to dehydration

The phytohormone abscisic acid (ABA) is de novo synthesized from 9-cis-epoxycarotenoids via three enzymatic steps. It is also produced via one-step hydrolysis of ABA glucose ester (ABA-GE) by BGLU18 (originally named AtBG1), a beta-glucosidase. It remained unclear how ABA-GE hydrolysis is induced by stresses or how the physiological impact of BGLU18-mediated ABA production on plant stress physiology. Han et al. (2020) propose that stress-responsive changes in endoplasmic reticulum (ER) body dynamics is a trigger of the activation of BGLU18 for ABA-GE hydrolysis. In addition, Han et al. (2020) demonstrated that BGLU18-mediated ABA-GE hydrolysis occurs locally at the epidermis of the petioles during the early stage of drought stress. This work clearly demonstrates that BGLU18-mediated ABA production has a distinct physiological impact from de novo ABA biosynthesis in terms of its spatial and temporal mode of action.