Effect of chitosan on tobacco mosaic virus (TMV) accumulation, hydrolase activity, and morphological abnormalities of the viral particles in leaves of N. tabacum L. cv. Samsun

Abstract

The effect of chitosan on the development of infection caused by Tobacco mosaic virus (TMV) in leaves of Nicotiana tabacum L. cv. Samsun has been studied. It was shown that the infectivity and viral coat protein content in leaves inoculated with a mixture of TMV (2 μg/mL) and chitosan (1 mg/mL) were lower in the early period of infection (3 days after inoculation), by 63% and 66% respectively, than in leaves inoculated with TMV only. Treatment of leaves with chitosan 24 h before inoculation with TMV also caused the antiviral effects, but these were less apparent than when the virus and polysaccharide were applied simultaneously. The inhibitory effects of the agent decreased as the infection progressed. Inoculation of leaves with TMV together with chitosan considerably enhanced the activity of hydrolases (proteases, RNases) in the leaves, in comparison with leaves inoculated with TMV alone. Electron microscope assays of phosphotungstic acid (PTA)-stained suspensions from infected tobacco leaves showed that, in addition to the normal TMV particles (18 nm in diameter, 300 nm long), these suspensions contained abnormal (swollen, "thin" and "short") virions. The highest number of abnormal virions was found in suspensions from leaves inoculated with a mixture of TMV and chitosan. Immuno-electron microscopy showed that "thin" virus particles, in contrast to the particles of normal diameter, lost the ability to bind to specific antiserum. It seems that the chitosan-induced activation of hydrolases stimulates the intracellular degradation of TMV particles and hence hydrolase activation may be considered to be one of the polysaccharide-mediated cellular defense mechanisms that limit virus accumulation in cells.

Chitosan Nanoparticles Inactivate Alfalfa Mosaic Virus Replication and Boost Innate Immunity in Nicotiana glutinosa Plants

“…Electron microscope examination revealed that the TMV particles were directly affected by nanoparticles, resulting in decreased viral particles, and the majority of them twisted together and tied into a bundle, leading to virus structure rupture [55,59]. In agreement with our results, the DAS-ELISA showed the efficacy of chitosan to control CMV, PVX, and TMV infections [51,58,60]. The authors suggested that chitosan increased plant resistance through enhancing ribonuclease activity and callose deposition as well as increasing the activity of hydrolases (proteases and RNases).…”

“…In this context, foliar application and treatment of tomato plants with ZnO NPs and Ag NPs reduced viral accumulation levels inside plant tissues and decreased disease severity [26,57]. In agreement with our results, chitosan nanoparticles might attach to virus particles, inhibit nucleic acid replication inside infected cells, as well as boost plant immunity and antioxidant defense systems [51,58]. Electron microscope examination revealed that the TMV particles were directly affected by nanoparticles, resulting in decreased viral particles, and the majority of them twisted together and tied into a bundle, leading to virus structure rupture [55,59].…”

“…At 20 dpi, the relative transcriptional levels were 1.75-, 4.03-, 6.43-, and 8.62-fold higher than mock-inoculated control in AMV-inoculated control, curative, protective, and inactivating treatments, respectively. In this regard, the antiviral activities of CDNPs have been ruled out in AMV-inoculated control N. glutinosa leaves, and the inhibitory effects of treatment (protective, curative, and inactivating) were attributed to the elicitation of the plant defense mechanisms and direct suppression of viral replication [23,51,56,58]. In agreement with these findings, previous studies showed that although the Cucumber mosaic virus did not significantly affect the expression levels of PAL, chitosan reduced the viral load and up-regulated PAL expression in infected tomato plants [51].…”

The Multifunctional Role of Chitosan in Horticultural Crops; A Review

“…Similarly, chitosan in formulation with plant growth promoting rhizobacteria (PGRP) conferred resistance to leaf curl virus in tomato plant [ 79 ]. Also, chitosan was found effective against squash mosaic virus (SMV) [ 80 , 81 ]. Furthermore, Chirkov et al [ 18 ] hypothesized that there might be some peculiar properties of the host plant which initiate the antiviral reaction(s) after chitosan treatment.…”

Inhibitory Effect of Chitosan and Phosphate Cross-linked Chitosan against Cucumber Mosaic Virus and Pepper Mild Mottle Virus

“…CS is also used as a conventional fungicide in both preharvest (Feliziani et al, 2015) and post-harvest applications (Sivakumar et al, 2016;Zhang et al, 2015). CS applicationinduced response against potato virus X and tomato mosaic virus was reported by (Chirkov et al, 2001;Jia et al, 2016;Nagorskaya et al, 2014). CS perception in the plant's variation in the ion fluxes and membrane depolarization (Iriti and Varoni, 2015) and also recognized by the plant as a pathogen-mimicking stimulus, but the identification of a CS receptor is still mysterious (Malerba and Cerana, 2016;Povero et al, 2011).…”