Chloroplast protection in plum pox virus-infected peach plants by L-2-oxo-4-thiazolidine-carboxylic acid treatments: effect in the proteome

Sharka, a disease caused by plum pox virus (PPV), has a significant economic impact on fruit tree production. In this work, we analysed the effect of (2,1,3)-benzothiadiazole (BTH) and L-2-oxo-4-thiazolidine-carboxylic acid (OTC) on plant growth and virus content. OTC reduced sharka symptom, stimulated plant growth and alleviated PPV-induced oxidative stress, indicated by a lack of changes in some oxidative stress parameters. PPV infection reduced chloroplast electron transport efficiency. However, in the presence of BTH or OTC, no changes in the chlorophyll fluorescence parameters were observed. PPV produced an alteration in chloroplast ultrastructure, giving rise to a decrease in starch contents that was less dramatic in OTC-treated plants. Furthermore, PPV reduced the abundance of proteins associated with photosynthesis, carbohydrate and amino acid metabolism and photorespiration. These changes did not take place in OTC-treated plants, and increases in the expression of proteins related with the aforementioned processes, including ADP-glucose pyrophosphorylase, were produced, which correlated with the lower decrease in starch contents observed in PPV-infected plants treated with OTC. The results suggested that OTC treatment provides protection to the photosynthetic machinery and/or the chloroplast metabolism in PPV-infected peaches. Thus, OTC could have practical implications in agriculture in improving the vigour of different plant species as well as in immunizing plants against pathogens.