title: An Arabidopsis homolog of importin β1 is required for ABA response and drought tolerance.
abstract: The import of proteins into the nucleus in response to drought is critical for mediating the reprogramming of gene expression that leads to drought tolerance. However, regulatory mechanisms involved in nuclear protein import remain largely unknown. Here, we have identified an Arabidopsis gene (AtKPNB1) as a homolog of human KPNB1 (importin β1). AtKPNB1 was expressed in multiple organs, and the protein was localized in the cytoplasm and nucleus. AtKPNB1 was able to facilitate nuclear import of a model protein. Null mutation of AtKPNB1 delayed development under normal growth conditions and increased sensitivity to abscisic acid (ABA) during seed germination and cotyledon development. Inactivation of AtKPNB1 increased stomatal closure in response to ABA, reduced the rate of water loss, and substantially enhanced drought tolerance. AtKPNB1 interacted with several importin α proteins, nucleoporin AtNUP62, and the Arabidopsis Ran proteins. Inactivation of AtKPNB1 did not affect the ABA responsiveness or the expression level or subcellular localization of ABI1, ABI2 or ABI5, key regulators of the ABA signaling pathway. Moreover, phenotypic analysis of epistasis revealed that AtKPNB1 modulates the ABA response and drought tolerance through a pathway that is independent of ABI1 and ABI5. Collectively, our results show that AtKPNB1 is an Arabidopsis importin β that functions in ABA signaling.
authors.affiliation: State Key Laboratory of Plant Cell & Chromosome Engineering, Center for Agricultural Research Resources, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, 286 Huaizhong Road, Shijiazhuang, Hebei 050021, China.
authors.forename: Yanjie
authors.initials: Y
authors.lastname: Luo
authors.forename: Zhijuan
authors.initials: Z
authors.lastname: Wang
authors.forename: Hongtao
authors.initials: H
authors.lastname: Ji
authors.forename: Hui
authors.initials: H
authors.lastname: Fang
authors.forename: Shuangfeng
authors.initials: S
authors.lastname: Wang
authors.forename: Lining
authors.initials: L
authors.lastname: Tian
authors.forename: Xia
authors.initials: X
authors.lastname: Li
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism* / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D000079922:Copper Transport Proteins; D003593:Cytoplasm / Q000378:metabolism; D055864:Droughts; D004843:Epistasis, Genetic; D018506:Gene Expression Regulation, Plant; D018525:Germination / Q000235:genetics; D009154:Mutation; D009997:Osmotic Pressure; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism; D054046:Plant Stomata / Q000502:physiology; D030821:Plants, Genetically Modified; D016601:RNA-Binding Proteins; D012639:Seeds / Q000235:genetics; D013312:Stress, Physiological; D028961:beta Karyopherins / Q000235:genetics / Q000378:metabolism; D020931:ran GTP-Binding Protein
chemical_list: C409743:ABI5 protein, Arabidopsis; D029681:Arabidopsis Proteins; C490178:At5g20010 protein, Arabidopsis; D050976:Basic-Leucine Zipper Transcription Factors; D027682:Cation Transport Proteins; D000079922:Copper Transport Proteins; C587771:KPNB1 protein, Arabidopsis; C424166:KPNB1 protein, human; D016601:RNA-Binding Proteins; D028961:beta Karyopherins; D000040:Abscisic Acid; C087434:ABI1 protein, Arabidopsis; C106443:ABI2 protein, Arabidopsis; D010749:Phosphoprotein Phosphatases; D020931:ran GTP-Binding Protein
keywords: ABA response; Arabidopsis thaliana; Importin β1; drought resistance; nuclear importin; nuclear proteins