ИСТИНА

Unlike animals, plant cells form a multicellular symplast in which neighbouring cells are connected via plasmodesmata (Pd), the unique nanopores piercing cell walls and characteristic only to plants. Through these structures, diffusion of low molecular weight metabolites and active transport of macromolecules occur, contributing to the functional integrity of plants. Recently, we proposed a mechanistic model of mature leaf Pd regulation according to which Pd-associated proteins (PdAPs) are classified as negative and positive regulators. Our studies of the Kunitz protease inhibitor-like protein (KPILP), which is encoded by the matryoshka gene, showed that this glycoprotein can be considered a positive regulator of Pd permeability. KPILP, which is not detected in intact leaves, is synthesized in cells only after exposure to abiotic and biotic stress. The increase in KPILP production leads to the activation of the intercellular transport of macromolecules. The mechanism of KPILP-induced Pd gating seems to be based on competition with negative PdAPs, which include Class 1 reversibly glycosylated polypeptide (C1RGP). We found that KPILP induction is accompanied by a decrease in the content of C1RGP in the cell and its displacement from the Pd. These results fit into our proposed mechanistic model of Pd regulation.