Stomatal cytokinesis defective2-dependent endocytic vesicular trafficking of abscisic acid.

Abscisic acid (ABA), a stressful phytohormone, is transported and signaled by clathrin-mediated endocytosis (CME) and clathrin-coated vesicles (CCVs). However, whether ABA promotes its cellular intake by CME and CCVs remains unknown. Here, this issue is first clarified by CME-mediated exogenous biotinylated ABA (bioABA) to localize in CCVs using three fluorescent macromolecules. BioABA has the physiological activity of ABA and may simulate the typical physiological effects of ABA during Arabidopsis seed germination and root growth. A binding analysis confirmed that both ABA and bioABA could specifically interact with SCD2 (stomatal cytokinesis defective2), key to CME and CCVs. As an application of bioABA and FM4-64 on AtSCD2-GFP transgenic Arabidopsis roots, exogenous bioABA was visually localized in the CME-mediated CCVs, which was promoted by SCD2 and ABA. Altogether, this study integrates ABA into SCD2-mediated CME and CCVs, providing a perspective understanding of ABA trafficking and signaling in plant growth and adaptation.