ИСТИНА

Plants generate a complex defence reaction in response to pathogen attacks that includes the emission of volatile organic compounds. Recently, we showed that methanol emitted by injured plants causes a phenotypically inconspicuous priming reaction in neighbouring plants i.e., the preparation of a plant receiver for a potential bacterial attack. The so-called methanol-inducible genes (MIGs) play a key role in such priming. Included among these genes are β-1,3-glucanase (BG), NCAPP (non-cell-autonomous pathway protein) and the previously unidentified gene MIG-21. In this study, we performed a search for a natural system to study the role of the intercellular transport of macromolecules in plant antibacterial immunity. Tobacco “sink” and “source” leaves fulfilled our requirements. The main difference between such leaves is the degree of plasmodesma "openness". In intact tobacco plants, only small upper leaves, also known as "sink" leaves, which are the acceptors of photoassimilates, are characterised by the presence of open plasmodesmata and intense intercellular transport. Mature, large tobacco leaves, i.e., "source" leaves, are the donors of photoassimilates. We compared the ability of tobacco “sink” and “source” leaves to support Agrobacterium tumefaciens growth and found no difference between them, although the leaves showed a significant difference in the transcriptional activity of some MIGs, such as BG and MIG-21. However, methanol dramatically enhanced the antibacterial immunity of the “sink” and “source” leaves, and this enhancement was accompanied by activation of the transcriptional activity of the NCAPP gene. We concluded that the elevated level of NCAPP and not the degree of open plasmodesmata plays a key role in the increase in plant antibacterial immunity. Although bacteria are mainly extracellular pathogens that do not need to transfer their genetic material into plant cells, the nucleocytoplasmic transport of their protein virulence factors is an important stage of plant cell colonisation. We found that NCAPP can suppress the nucleocytoplasmic transport of bacterial virulence factors. We concluded that methanol controls plant immunity by affecting the nucleocytoplasmic transport and intercellular transport of macromolecules.