Chitosan Upregulates the Genes of the ROS Pathway and Enhances the Antioxidant Potential of Grape (Vitis vinifera L. ‘Touriga Franca’ and ’Tinto Cão’) Tissues

Abstract

Chitosan is an environmentally-friendly active molecule that has been explored for numerous agricultural uses. Its use in crop protection is well-known, however, other properties, such as bioactivity, deserve attention. Moreover, the modes of actions of chitosan remain to be elucidated. The present study assessed the levels of total phenolic compounds, the antioxidant potential, and the expression of reactive oxygen species (ROS) scavenging genes in the berries (skins and seeds), leaves, cluster stems, and shoots upon chitosan application on two red grapevine varieties (Touriga Franca and Tinto Cão). The application of chitosan on the whole vine before and after veraison led to the increased levels of polyphenols, anthocyanins, and tannins in Tinto Cão berries, and polyphenols and tannins in Touriga Franca berries, respectively. CUPric Reducing Antioxidant Capacity (CUPRAC) and Ferric Reducing Antioxidant Power (FRAP) assays indicated an increase in the antioxidant potential of berries. With the exception of ascorbate peroxidase (APX), all the ROS pathway genes tested, i.e., iron-superoxide dismutase (Fe-SOD), copper-zinc-superoxide dismutase (Cu/Zn-SOD), catalase (CAT), glutathione reductase (GR), glutaredoxin (Grx), respiratory burst oxidase (Rboh), amine oxidase (AO), peroxidase (POD) and polyphenol oxidase (PPO), were found up-regulated in chitosan-treated berries. Results from the analyses of leaves, stems, and shoots revealed that chitosan not only induced the synthesis of phenolic compounds but also acted as a facilitator for the transfer of polyphenols from the leaves to the berries.

Chitosan Application in Vineyards (Vitis vinifera L. cv. Tinto Cão) Induces Accumulation of Anthocyanins and Other Phenolics in Berries, Mediated by Modifications in the Transcription of Secondary Metabolism Genes

“…Previous studies also demonstrated that continuous chitosan application improved polyphenolic content and wine antioxidant potential when compared with the traditional fungicide treatments [7], whereas preharvest application showed no differences in these parameters [10]. Our recent study further suggested improved antioxidant potential upon chitosan application in Vitis vinifera L. [11].…”

“…One report demonstrated some elicitation potential in Hypericum perforatum root cultures on xanthone biosynthesis [40]. The same amount of acetic acid solution (0.01% aqueous solution) was applied on the control grapevine in the present study to confirm the mechanism of the chitosan effect, which has been unanswered in our previous report [11]. It may be that the difference in xanthone synthesis in cultures may be due to change in culture medium properties by acetic acid and will need further investigation [40].…”

“…Improved metabolites in plants may lead to increase in antioxidant activity towards higher plant fitness by scavenging the toxic reactive oxygen species [11]. Catalase and Ascorbate peroxidase gene expression was recorded with no significant change in treated plants in comparison to control (Figure 2i,j).…”

“…The present study strengthens previous findings and validates that 0.01% chitosan application promotes secondary metabolism, highlighting that elicitor concentration and timing of application are very important in order to get optimum effects. Our previous study [11] has shown improved metabolites accumulation as well as antioxidant potential in different phenotypic stages where control grapevines were maintained without any acetic acid spray. The present study incorporated a similar amount of acetic acid (0.01% acetic acid in water) solution application in control grapevines, followed by identification of different monomeric anthocyanins as well as rutin, catechin, chlorogenic acid and quercetin-3-O-galactoside.…”

“…Tinto Cão. Control grapevines were treated with 0.01% acetic acid solution to ensure the invigorated effect of chitosan; which was left behind in our previous study [11]. The study was complemented with expression studies of target genes encoding key enzymes of secondary metabolite synthesis and transport in grape berry skins, including phenylalanine ammonia lyase (PAL) that catalyzes the first step of phenylpropanoid biosynthesis, UFGT that mediates the limiting step towards anthocyanin biosynthesis and MATE1 that transports anthocyanins to the vacuole.…”