SPY Interacts With Tubulin and Regulates Abscisic Acid‐Induced Stomatal Closure in Arabidopsis

Sugars are important both as an energy source and a signaling cue. In <i>Arabidopsis thaliana,</i> SPINDLY (SPY) is the <i>bona fide</i> <i>O</i>-fucosylation transferase that links sugar with various plant growth and development processes. Previously, <i>spy</i> was shown to display a strong salt and drought tolerance phenotype. Herein we confirmed the phenotype and further studied its mechanism. We found that abscisic acid (ABA) elevated <i>SPY</i> expression in guard cells, and SPY is involved in ABA-induced stomatal closure. We show that SPY regulates the rearrangement of the microtubule cytoskeleton in guard cells. Moreover, ABA-induced microtubule reorganization is enhanced in <i>spy</i> mutants. Mechanistically, SPY interacts with α-tubulin1 (TUA1) in both yeast-two hybrid, bimolecular fluorescence complementation and split luciferase complementation imaging assays, indicating that TUA1 may be <i>O</i>-fucosylated by SPY. Our work is in line with the notion that SPY has many substrates involved in diverse processes in plants, and also unearths a key mechanism how glycosylation regulates the stomata movement via the microtubule cytoskeleton.