ABA receptor abundance, thus ABA sensitivity, is regulated by ALIX ($) (Plant Cell)

To balance water loss and CO₂ assimilation, stomatal aperture is tightly controlled in accordance with environmental changes, mediated by ABA signaling. Here, García-León et al. found that ABA sensitivity and stomatal aperture are regulated by the trafficking and vacuolar degradation of ABA receptors (PYLs). This turnover is regulated by an ESCART-III-associated protein ALIX, which is able to bind PYLs directly, and ALIX-mediated PYL turnover may be responsive to ABA, in a form of negative feedback. This intriguing study illustrates not just a relationship between endosomal trafficking and ABA signaling pathway, but also a key molecular mechanism responsible for adaptation of plants to water-deficient environments. (Summary by Nanxun Qin) Plant Cell 10.1105/tpc.19.00399