ИСТИНА

The plasmodesma (PD) is a unique cellular structure that intersects with the cell wall and connects the cytoplasm and the endoplasmic reticulum of neighbouring cells. Plants that utilize PD undergo holistic reactions during their growth process and in response to stressful environmental factors. The mechanism underlying the relationship between stress and PD function is not completely understood. Recently, we identified a protein (KPILP, Kunitz protease inhibitor-like protein) that bears some homology to the Kunitz protease inhibitor, the expression of which increases dramatically in response to stressful events 1. Here, we found that KPILP is a glycoprotein and has a signalling sequence that directs the protein to the cell wall via the membrane system of the Golgi apparatus (GA). Experiments that used 2 x GFP as a tracer molecule have shown that KPILP increases PD gating. To study the involvement of the GA in KPILP biogenesis, we used two experimental approaches: (a) site-directed mutagenesis, which was used to inhibit the N-glycosylation of KPILP; (b) attachment of the C-terminus of KPILP to the targeted KDEL sequence, which prevented its secretion via the GA. The results confirmed the important role of the GA, not only in KPILP intracellular traffic but also in terms of its ability to “open” the PD. It was shown that carbohydrate molecules must be present in KPILP for it to perform its function. We believe that KPILP, which is absent in intact leaves, only appears in the cell after exposure to abiotic and biotic stress; during times of stress, it “opens” the PD to ensure the enhanced intercellular transport of signalling molecules into the surrounding tissues and of photosynthesis products to the areas of plant growth. This study was performed with financial support from the Russian Foundation for Basic Research (project Nos. 18-34-00576 and 17-29-08012).