Comparative Evaluation of Biochemical Changes in Tomato (Lycopersicon esculentum Mill.) Infected by Alternaria alternata and Its Toxic Metabolites (TeA, AOH, and AME)

Abstract

In the present study, we have evaluated the comparative biochemical defense response generated against Alternaria alternata and its purified toxins viz. alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TeA). The necrotic lesions developed due to treatment with toxins were almost similar as those produced by the pathogen, indicating the crucial role of these toxins in plant pathogenesis. An oxidative burst reaction characterized by the rapid and transient production of a large amount of reactive oxygen species (ROS) occurs following the pathogen infection/toxin exposure. The maximum concentration of hydrogen peroxide (H2O2) produced was reported in the pathogen infected samples (22.2-fold) at 24 h post inoculation followed by TeA (18.2-fold), AOH (15.9-fold), and AME (14.1-fold) in treated tissues. 3,3′- Diaminobenzidine staining predicted the possible sites of H2O2 accumulation while the extent of cell death was measured by Evans blue dye. The extent of lipid peroxidation and malondialdehyde (MDA) content was higher (15.8-fold) at 48 h in the sample of inoculated leaves of the pathogen when compared to control. The cellular damages were observed as increased MDA content and reduced chlorophyll. The activities of antioxidative defense enzymes increased in both the pathogen infected as well as toxin treated samples. Superoxide dismutase (SOD) activity was 5.9-fold higher at 24 h post inoculation in leaves followed by TeA (5.0-fold), AOH (4.1-fold) and AME (2.3-fold) treated leaves than control. Catalase (CAT) activity was found to be increased upto 48 h post inoculation and maximum in the pathogen challenged samples followed by other toxins. The native PAGE results showed the variations in the intensities of isozyme (SOD and CAT) bands in the pathogen infected and toxin treated samples. Ascorbate peroxidase (APx) and glutathione reductase (GR) activities followed the similar trend to scavenge the excess H2O2. The reduction in CAT activities after 48 h post inoculation demonstrate that the biochemical defense programming shown by the host against the pathogen is not well efficient resulting in the compatible host-pathogen interaction. The elicitor (toxins) induced biochemical changes depends on the potential toxic effects (extent of ROS accumulation, amount of H2O2 produced). Thus, a fine tuning occurs for the defense related antioxidative enzymes against detoxification of key ROS molecules and effectively regulated in tomato plant against the pathogen infected/toxin treated oxidative stress. The study well demonstrates the acute pathological effects of A. alternata in tomato over its phytotoxic metabolites.

Omics-Based Mechanistic Insight Into the Role of Bioengineered Nanoparticles for Biotic Stress Amelioration by Modulating Plant Metabolic Pathways

“…AB + SNP exhibited 68.68, 96, and 212.5% increase in chlorophyll content and fresh and dry weight, respectively, as compared to AB alone (Figures 1Ed,e). Loss of photosynthetic pigments is one of the major biochemical changes a plant undergoes during Alternaria infection (Meena et al, 2016). Increase in chlorophyll content in AB + SNP in comparison to AB alone showed the increased disease resistance of plant toward disease after treatment with SNPs.…”

Mycotoxin Contamination of Beverages Obtained from Tropical Crops

“…At least one report has described how to apply a risk management standard directly (i.e., AS/NZS 4360) to the beverage industry [264]. Physical (foreign material, e.g., insect fragments), chemical (water content, total solids, soluble solids, pH and acidity), microbiological (i.e., mycelial filament count) [190] and biochemical (H 2 O 2 production, cellular damage and death) [194] properties have been described for one fruit that was associated with Alternaria toxins.…”

Growth and Physiological Responses of Adenophora triphylla (Thunb.) A.DC. Plug Seedlings to Day and Night Temperature Regimes

“…However, more studies should focus on the response of antioxidant enzymes under a moderate temperature range between chilling and heat. Furthermore, for each kind of antioxidant enzyme, isozymes catalyzing the same chemical reaction with different structures are activated differentially in detoxifying ROS process under various conditions [32][33][34]. Clearly, an in-depth study of the expression and activity of the various antioxidant isozymes under temperature regimes is necessary to figure out antioxidant system and self-defending mechanism in plant.…”

“…And the band intensity was closely dependent on the activities of isozymes. Hence, this method was always used to assess the activity of isozymes together with quantitative analysis of antioxidant enzyme activities [32,37,38].…”