EFFECTS OF OLIGOCHITOSANS ON TOBACCO CELLS AND ROLE OF ENDOGENOUS NITRIC OXIDE BURST IN THE RESISTANCE OF TOBACCO TO TOBACCO MOSAIC VIRUS
X.M. Zhao, X.P. She, W. Yu, X.M. Liang, Y.G. Du
Binding to tobacco cells of oliogochitosan labeled with the fluorophore 2-aminoacidone (2-AMAC) was investigated using laser scanning confocal microscopy (LSCM). Production of NO in epidermal tobacco cells treated with oligochitosan was investigated by epidermal strip bioassay and LSCM, using the cell-permeable fluorophore diaminofluorescein diacetate (DAF-2D). Binding of the labeled oligochitosan to cell walls and membranes of tobacco cells was directly observed by LSCM. Binding antagonist assays showed that unlabeled oligsaccharides apart from oligochitosn did not inhibit the observed binding of labeled oligochitosan to cell walls and membranes. Treatment of epidermal tobacco cells with oligochitosan resulted in a strong increase of intracellular NO. Oligochitosan and the NO donor SNP induced a defense reaction against Tobacco mosaic virus (TMV), increased PAL activity and elevated PAL mRNA level. Co-treatment of oligochitosan and NO (scavenger CPTIO) blocked the inducing resistance indicating that the defense response induced by oligochitosan was connected with the NO pathway.