Functional requirement of the Arabidopsis importin-α nuclear transport receptor family in autoimmunity mediated by the NLR protein SNC1

IMPORTIN-alpha 3/MOS6 (MODIFIER OF SNC1, 6) is one of nine importin-alpha isoforms in Arabidopsis that recruit nuclear localization signal-containing cargo proteins to the nuclear import machinery. IMP-alpha 3/MOS6 is required genetically for full autoimmunity of the nucleotide-binding leucine-rich repeat immune receptor mutant snc1 (suppressor of npr1-1, constitutive 1) and MOS6 also contributes to basal disease resistance. Here, we investigated the contribution of the other importin-alpha genes to both types of immune responses, and we analyzed potential interactions of all importin-alpha isoforms with SNC1. By using reverse-genetic analyses in Arabidopsis and protein-protein interaction assays in Nicotiana benthamiana, we provide evidence that among the nine alpha-importins in Arabidopsis, IMP-alpha 3/MOS6 is the main nuclear transport receptor of SNC1, and that IMP-alpha 3/MOS6 is required selectively for autoimmunity of snc1 and basal resistance to mildly virulent Pseudomonas syringae in Arabidopsis.

Automated summary

IMPORTIN-alpha 3/MOS6 is a key factor in regulating immune responses in Arabidopsis, primarily responsible for the nuclear transport of SNC1, playing an important role in autoimmunity and basal disease resistance.