Methanol-Inducible Gene (MIG) 21 Encodes a Nucleolus-Localized Protein That Stimulates Viral Intercellular Transport and Downregulates Nuclear Import.

The mechanical damage of plant tissues leads to the activation of methanol production and its release into the atmosphere. The gaseous methanol or vapors emitted by the damaged plant induce resistance in neighboring intact plants to bacterial pathogens but create favorable conditions for viral infection spread. Among the methanol-inducible genes (MIGs), most are associated with plant defense and intercellular transport. Here, we characterize , which encodes a 209 aa protein (NbMIG21p) that does not share any homology with annotated proteins. NbMIG21p was demonstrated to contain a nucleolus localization signal (NoLS). Colocalization studies with fibrillarin and coilin, nucleolus and Cajal body marker proteins, revealed that NbMIG21p is distributed among these subnuclear structures. Our results show that recombinant NbMIG21 possesses DNA-binding properties. Similar to a gaseous methanol effect, an increased expression leads to downregulation of the nuclear import of proteins with nuclear localization signals (NLSs), as was demonstrated with the GFP-NLS model protein. Moreover, upregulated expression facilitates tobacco mosaic virus (TMV) intercellular transport and reproduction. We identified an promoter (PrMIG21) and showed that it is methanol sensitive; thus, the induction of mRNA accumulation occurs at the level of transcription. Our findings suggest that methanol-activated might participate in creating favorable conditions for viral reproduction and spread.