Centro Nacional de Biotecnología, 28049 Madrid, Spain.
Aix Marseille Université, Commissariat à l'Energie Atomique, Centre National de la Recherche Scientifique, BIAM, UMR7265, SAVE, Saint Paul-Lez-Durance, France.
Plant Cell. 2019 Oct;31(10):2411-2429. doi: 10.1105/tpc.19.00399. Epub 2019 Jul 30.
The plant endosomal trafficking pathway controls the abundance of membrane-associated soluble proteins, as shown for abscisic acid (ABA) receptors of the PYRABACTIN RESISTANCE1/PYR1-LIKE/REGULATORY COMPONENTS OF ABA RECEPTORS (PYR/PYL/RCAR) family. ABA receptor targeting for vacuolar degradation occurs through the late endosome route and depends on FYVE DOMAIN PROTEIN REQUIRED FOR ENDOSOMAL SORTING1 (FYVE1) and VACUOLAR PROTEIN SORTING23A (VPS23A), components of the ENDOSOMAL SORTING COMPLEX REQUIRED FOR TRANSPORT-I (ESCRT-I) complexes. FYVE1 and VPS23A interact with ALG-2 INTERACTING PROTEIN-X (ALIX), an ESCRT-III-associated protein, although the functional relevance of such interactions and their consequences in cargo sorting are unknown. In this study we show that Arabidopsis () 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 activity, partial loss-of-function 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 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 mutants. Our findings unveil a negative feedback mechanism triggered by ABA that acts via ALIX to control the accumulation of specific PYR/PYL/RCAR receptors.
植物内体运输途径控制着膜相关可溶性蛋白的丰度，正如脱落酸（ABA）受体的PYRABACTIN RESISTANCE1/PYR1-LIKE/REGULATORY COMPONENTS OF ABA RECEPTORS（PYR/PYL/RCAR）家族所显示的那样。ABA 受体通过晚期内体途径靶向液泡降解，这依赖于 FYVE DOMAIN PROTEIN REQUIRED FOR ENDOSOMAL SORTING1（FYVE1）和 VACUOLAR PROTEIN SORTING23A（VPS23A），它们是 ENDOSOMAL SORTING COMPLEX REQUIRED FOR TRANSPORT-I（ESCRT-I）复合物的组成部分。FYVE1 和 VPS23A 与 ALG-2 INTERACTING PROTEIN-X（ALIX）相互作用，ALIX 是 ESCRT-III 相关蛋白，尽管这种相互作用的功能相关性及其在货物分拣中的后果尚不清楚。在这项研究中，我们表明拟南芥（Arabidopsis thaliana）ALIX 直接与晚期内体中的 ABA 受体结合，促进其降解。ALIX 功能受损导致内体定位改变和 ABA 受体积累增加。与此活动一致，部分功能丧失的 突变体在生长和气孔关闭过程中表现出对 ABA 的超敏反应，揭示了 ESCRT 机制在通过气孔控制水分损失中的作用。在 PYR/PYL/RCAR 活性受损的 植物中，ABA 超敏反应受到抑制，这与 ALIX 通过控制 ABA 受体稳定性主要影响 ABA 反应一致。ALIX-1 突变蛋白与 VPS23A 和 ABA 受体的相互作用减少，为 突变体中 ABA 超敏反应提供了分子基础。我们的发现揭示了一种由 ABA 触发的负反馈机制，该机制通过 ALIX 控制特定 PYR/PYL/RCAR 受体的积累。
