Abscisic Acid Triggers the Endocytosis of the Arabidopsis KAT1 K+ Channel and Its Recycling to the Plasma Membrane

Abstract

Membrane vesicle traffic to and from the plasma membrane is essential for cellular homeostasis in all eukaryotes. In plants, constitutive traffic to and from the plasma membrane has been implicated in maintaining the population of integral plasma-membrane proteins and its adjustment to a variety of hormonal and environmental stimuli. However, direct evidence for evoked and selective traffic has been lacking. Here, we report that the hormone abscisic acid (ABA), which controls ion transport and transpiration in plants under water stress, triggers the selective endocytosis of the KAT1 K+ channel protein in epidermal and guard cells. Endocytosis of the K+ channel from the plasma membrane initiates in concert with changes in K+ channel activities evoked by ABA and leads to sequestration of the K+ channel within an endosomal membrane pool that recycles back to the plasma membrane over a period of hours. Selective K+ channel endocytosis, sequestration, and recycling demonstrates a tight and dynamic control of the population of K+ channels at the plasma membrane as part of a key plant signaling and response mechanism, and the observations point to a role for channel traffic in adaptive changes in the capacity for osmotic solute flux of stomatal guard cells.

Reconstitution of Abscisic Acid Signaling from the Receptor to DNA via bHLH Transcription Factors

“…Rapid events occur within seconds to promote stomatal closure through physiological cellular responses, including Ca 2+ elevation and regulation of ion channels and pump activities by protein phosphorylation and dephosphorylation . Slow events are thought to inhibit stomatal reopening in the late periods after the increase in ABA concentration and are mediated by gene expression, ion channel modifications, and intracellular relocation of the transporter proteins (Sutter et al, 2006(Sutter et al, , 2007Eisenach, et al, 2012). AKS1 dissociation from the KAT1 promoter reconstituted in this study most likely mediates late events through a decrease in the population of KAT1 proteins in the plasma membrane in coordination with KAT1 endocytosis in response to ABA (Sutter et al, 2007).…”

“…Slow events are thought to inhibit stomatal reopening in the late periods after the increase in ABA concentration and are mediated by gene expression, ion channel modifications, and intracellular relocation of the transporter proteins (Sutter et al, 2006(Sutter et al, , 2007Eisenach, et al, 2012). AKS1 dissociation from the KAT1 promoter reconstituted in this study most likely mediates late events through a decrease in the population of KAT1 proteins in the plasma membrane in coordination with KAT1 endocytosis in response to ABA (Sutter et al, 2007). Guard cells are shown to have a capability to create "stress memory" to maintain closed stomata, likely through the regulation of gene expression (Virlouvet and Fromm, 2015).…”

Binding of SEC11 Indicates Its Role in SNARE Recycling after Vesicle Fusion and Identifies Two Pathways for Vesicular Traffic to the Plasma Membrane

“…Nonetheless, a number of functional differences between SYP121 and SYP122 have surfaced. SYP121 has unique roles in responses to drought and the water stress hormone abscisic acid (Leyman et al, 1999;Sutter et al, 2007;Eisenach et al, 2012), and it facilitates targeted vesicle traffic for defense against pathogen attack . Furthermore, SYP121 uniquely interacts with K + channels to facilitate the uptake of the solute for cell expansion and plant growth (Honsbein et al, 2009Grefen et al, 2010a).…”

Adaptor Protein Complex 2–Mediated Endocytosis Is Crucial for Male Reproductive Organ Development in Arabidopsis

“…The colocalization of PIN1/2 and clathrin to the PM has been demonstrated in Arabidopsis thaliana root cells (Dhonukshe et al, 2007). In addition, homeostasis of K + is also modulated by an endocytosis-mediated regulation of potassium channel levels at the PM (Sutter et al, 2007). However, it remains elusive as to how broadly endocytosis is involved in regulating cellular processes in plants.…”