WD40 repeat-containing proteins (WD40 proteins) serve as versatile scaffolds for protein–protein interactions, modulating a variety of cellular processes such as plant stress and hormone responses. Here we report the identification of a WD40 protein, XIW1 (for XPO1-interacting WD40 protein 1), which positively regulates the abscisic acid (ABA) response in Arabidopsis. XIW1 is located in the cytoplasm and nucleus. We found that it interacts with the nuclear transport receptor XPO1 and is exported by XPO1 from the nucleus. Mutation of XIW1 reduces the induction of ABA-responsive genes and the accumulation of ABA Insensitive 5 (ABI5), causing mutant plants with ABA-insensitive phenotypes during seed germination and seedling growth, and decreased drought stress resistance. ABA treatment upregulates the expression of XIW1, and both ABA and abiotic stresses promote XIW1 accumulation in the nucleus, where it interacts with ABI5. Loss of XIW1 function results in rapid proteasomal degradation of ABI5. Taken together, these findings suggest that XIW1 is a nucleocytoplasmic shuttling protein and plays a positive role in ABA responses by interacting with and maintaining the stability of ABI5 in the nucleus.

包含WD40重复序列的蛋白质（WD40蛋白质）可作为蛋白质与蛋白质相互作用的多功能支架，调节多种细胞过程，例如植物胁迫和激素反应。在这里，我们报告鉴定WD40蛋白质XIW1（用于XPO1相互作用的WD40蛋白质1），该蛋白质正调控拟南芥中的脱落酸（ABA）反应。XIW1位于细胞质和细胞核中。我们发现它与核转运受体XPO1相互作用，并由XPO1从核中输出。XIW1的突变减少了ABA反应基因的诱导和ABA不敏感5（ABI5）的积累，导致种子发芽和幼苗生长期间具有ABA不敏感表型的突变植物，并降低了干旱胁迫抗性。ABA处理可上调XIW1的表达，ABA和非生物胁迫均可促进XIW1在细胞核中积累，并与A​​BI5相互作用。XIW1功能的丧失导致ABI5的蛋白酶体快速降解。综上所述，这些发现表明XIW1是一种核质穿梭蛋白，并通过与核中的ABI5相互作用并保持其稳定性而在ABA反应中发挥积极作用。