García-León M, Cuyas L, Abd El-Moneim D, Rodriguez L, Belda-Palazon B, Sánchez-Quant E, Fernández Y, Roux B, Zamarreño AM, Garcia-Mina JM, Nussaume L, Rodriguez PL, Paz-Ares J, Leonhardt N, Rubio V.
Abstract
The plant endosomal trafficking pathway controls abundance of membrane-associated soluble proteins, as shown for abscisic acid (ABA) receptors (PYR/PYL/RCAR). ABA receptor targeting for vacuolar degradation occurs through the late endosome route and depends on FYVE1 and VPS23A, components of endosomal sorting complex required for transport (ESCRT)-I complexes. FYVE1 and VPS23A interact with ALIX, an ESCRT-III-associated protein, although the functional relevance of such interactions and their consequences in cargo sorting are unknown. Here we show that ALIX directly binds to ABA receptors in late endosomes, promoting their degradation. Impaired ALIX function leads to altered endosomal localization and increased accumulation of ABA receptors. In line with this, partial loss-of-function alix-1 mutants display ABA hypersensitivity during growth and stomatal closure, unveiling a role for the ESCRT machinery in the control of water loss through stomata. ABA hypersensitive responses are suppressed in alix-1 plants impaired in PYR/PYL/RCAR activity, in accordance with ALIX affecting ABA responses primarily by controlling ABA receptor stability. ALIX-1 mutant protein displays reduced interaction with VPS23A and ABA receptors, providing a molecular basis for ABA hypersensitivity in alix-1 mutants. Our findings unveil a negative feedback mechanism triggered by ABA acting via ALIX to control the accumulation of specific PYR/PYL/RCAR receptors.
doi: 10.1105/tpc.19.00399.