Acts as negative effector of drought tolerance. Involved in the regulation of stomatal closure and in the abscisic acid (ABA)-mediated pathway that lead to drought tolerance. Does not directly mediate nuclear import of ABI1 and ABI2 which are key regulators of the ABA signaling pathway. May be involved in nuclear translocation of other type 2C protein phosphatases that mediate ABA signaling. Forms a complex with the importin subunits alpha IMPA1 or IMPA2, the nucleoporin NUP62 and the Ran-GTP-binding proteins RAN1, RAN2 or RAN3. Expressed in roots, cotyledons, leaves, stems, petals, stamen, stigma, siliques, embryos and guard cells. Delayed development and flowering, reduced length of leaves, stems and siliques, increased sensitivity to abscisic acid (ABA) and increased drought tolerance. Belongs to the importin beta family. Importin beta-1 subfamily.