SEC16A/MAG5-mediated ER export shapes ABA receptor homeostasis
The phytohormone abscisic acid (ABA) controls plant adaptation to environmental stress through PYR/PYL/RCAR receptors. Regulated receptor turnover through ubiquitination and endosomal trafficking, including ESCRT-dependent vacuolar degradation, is a major mechanism controlling ABA signalling. However, whether ABA receptor homeostasis is established during the early secretory pathway remains…
Abscisic acid (ABA) plays a crucial role in plant adaptation to stress by regulating PYR/PYL/RCAR receptors. These receptors are controlled through ubiquitination and endosomal trafficking, including ESCRT-dependent degradation in the vacuole. However, it was previously unclear if ABA receptor homeostasis is established during the early secretory pathway. To investigate this, researchers employed cell biology and biochemical techniques to determine the role of the SEC16A (MAG5) protein in ABA receptor homeostasis.
The study found that SEC16A is essential for the proper trafficking and homeostasis of ABA receptors PYR1 and PYL4, which are associated with the endoplasmic reticulum (ER) and Golgi apparatus (GA). Genetic, cell biological, and pharmacological analyses revealed that loss of MAG5 resulted in intracellular receptor accumulation, impaired trafficking towards late endosomal compartments, and heightened ABA signaling.
Importantly, this disruption did not affect the normal levels of endogenous ABA. The findings demonstrate that the early secretory pathway is integral to the ABA signaling network and that MAG5-mediated ER export plays a crucial role in shaping ABA receptor homeostasis by coordinating receptor trafficking throughout the entire endomembrane system. This study highlights the ER as a key regulatory compartment for ABA receptor homeostasis.
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