SAD2 (super sensitive to ABA and drought 2) encodes an importin beta-domain family protein likely to be involved in nuclear transport in ABA signaling. Subcellular localization of GFP-tagged SAD2 showed a predominantly nuclear localization, consistent with a role for SAD2 in nuclear transport. Mutation of SAD2 in Arabidopsis alters abscisic acid sensitivity. SAD2 was ubiquitously expressed at low levels in all tissues except flowers. SAD2 expression was not induced by ABA or stress. Loss of function mutations in SAD2 exhibit increased tolerance for UV stress, increased production of UV protective secondary metabolites and suppression of nuclear localization of MYB4 (a repressor of UV stress response genes). Regulates microRNA activity. Defective trichome activity.
Functions probably in nuclear protein import, either by acting as autonomous nuclear transport receptor or as an adapter-like protein in association with other importin subunits (Probable). Involved in the regulation of the abscisic acid (ABA)-mediated pathway in response to cold or salt stress (PubMed:16889648). Involved in UV-B responses by regulating accumulation of UV-absorbing pigments through mediation of MYB4 nuclear transport (PubMed:17993626). Involved in trichome initiation by controlling GL1, GL2, GL3 and TTG1 transcription and may affect an upstream regulator of GL3 and disrupt complex function (PubMed:18713401, PubMed:19234066). Acts as a negative regulator miRNA activity by regulating miRNA loading into AGO1 complexes (PubMed:21984696).