Nicotiana benthamiana Class 1 Reversibly Glycosylated Polypeptides Suppress Tobacco Mosaic Virus Infection

Nicotiana benthamiana 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 Nicotiana benthamiana methanol-inducible genes (MIGs), most are associated with plant defense and intercellular transport. Here, we characterize NbMIG21, 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 NbMIG21 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 NbMIG21 expression facilitates tobacco mosaic virus (TMV) intercellular transport and reproduction. We identified an NbMIG21 promoter (PrMIG21) and showed that it is methanol sensitive; thus, the induction of NbMIG21 mRNA accumulation occurs at the level of transcription. Our findings suggest that methanol-activated NbMIG21 might participate in creating favorable conditions for viral reproduction and spread.

Nanoplatforms for the Delivery of Nucleic Acids into Plant Cells

Nanocarriers are widely used for efficient delivery of different cargo into mammalian cells; however, delivery into plant cells remains a challenging issue due to physical and mechanical barriers such as the cuticle and cell wall. Here, we discuss recent progress on biodegradable and biosafe nanomaterials that were demonstrated to be applicable to the delivery of nucleic acids into plant cells. This review covers studies the object of which is the plant cell and the cargo for the nanocarrier is either DNA or RNA. The following nanoplatforms that could be potentially used for nucleic acid foliar delivery via spraying are discussed: mesoporous silica nanoparticles, layered double hydroxides (nanoclay), carbon-based materials (carbon dots and single-walled nanotubes), chitosan and, finally, cell-penetrating peptides (CPPs). Hybrid nanomaterials, for example, chitosan- or CPP-functionalized carbon nanotubes, are taken into account. The selected nanocarriers are analyzed according to the following aspects: biosafety, adjustability for the particular cargo and task (e.g., organelle targeting), penetration efficiency and ability to protect nucleic acid from environmental and cellular factors (pH, UV, nucleases, etc.) and to mediate the gradual and timely release of cargo. In addition, we discuss the method of application, experimental system and approaches that are used to assess the efficiency of the tested formulation in the overviewed studies. This review presents recent progress in developing the most promising nanoparticle-based materials that are applicable to both laboratory experiments and field applications.