Deciphering Prunus Responses to PPV Infection: A Way toward the Use of Metabolomics Approach for the Diagnostic of Sharka Disease

Abstract

Sharka disease, caused by Plum pox virus (PPV), induces several changes in Prunus. In leaf tissues, the infection may cause oxidative stress and disrupt the photosynthetic process. Moreover, several defense responses can be activated after PPV infection and have been detected at the phytohormonal, transcriptomic, proteomic, and even translatome levels. As proposed in this review, some responses may be systemic and earlier to the onset of symptoms. Nevertheless, these changes are highly dependent among species, variety, sensitivity, and tissue type. In the case of fruit tissues, PPV infection can modify the ripening process, induced by an alteration of the primary metabolism, including sugars and organic acids, and secondary metabolism, including phenolic compounds. Interestingly, metabolomics is an emerging tool to better understand Prunus–PPV interactions mainly in primary and secondary metabolisms. Moreover, through untargeted metabolomics analyses, specific and early candidate biomarkers of PPV infection can be detected. Nevertheless, these candidate biomarkers need to be validated before being selected for a diagnostic or prognosis by targeted analyses. The development of a new method for early detection of PPV-infected trees would be crucial for better management of the outbreak, especially since there is no curative treatment.

Modeling the Impact of Agricultural Mitigation Measures on the Spread of Sharka Disease in Sweet Cherry Orchards

“…Therefore, growers should have simple and feasible technological monitoring mechanisms to detect the virus in their orchards, especially to detect asymptomatic trees, which are a constant reservoir of the disease. From an agronomic point of view, the use of molecular tools to provide an early diagnostic of the disease in the orchard should be implemented routinely [46,47]. Another diagnostic tool that needs to be studied further is the use of drones to detect symptomatic trees, as these technologies are becoming widely used and have already been useful for other sweet cherry diseases [48].…”

Physiological and Biochemical Responses Induced by Plum Pox Virus and Plum Bark Necrosis Steam Pitting Associated Virus in Tuscany Autochthonous Plum cv. Coscia di Monaca

“…Compared to the large number of diagnostic and molecular characterization studies of plant viruses, fewer investigations have been carried out on the effects of these pathogens on plant physiology and metabolism. However, previous studies have shown that PPV infection produced ultrastructure alterations in Prunus cells, affecting the thylakoids, plastoglobolus, granal, and starch content and indicating that the chloroplast is the most affected cell organelle [ 13 , 22 , 23 , 35 ]. These changes were associated with severe detrimental effects of PPV on photosynthesis and carbohydrate metabolism, affecting photosystem II (PSII), directly or indirectly, by decreasing the amount of rubisco, oxygen-evolving enhancer, and PSII stability factors [ 36 ].…”

“…The harmful PPV effects were due to oxidative stress manifested as lipid peroxidation, protein oxidation, electrolyte leakage, the accumulation of hydrogen peroxide, and an imbalance in the antioxidant systems [ 35 , 37 , 38 ]. However, it should be noted that some conflicting results on the physiological alterations and damage to Prunus caused by PPV infection have been reported, likely due to a combination of variables, including metabolic differences among the plant species studied and differences in the process of infection, the level of PPV infection, the time of sampling, and the conditions under which the plants were grown [ 23 , 39 ]. Importantly, all previous investigations were carried out under controlled conditions.…”

“…Although some studies have shown that in the case of fruit tissues, PPV infection can modify the ripening process via an alteration of the primary metabolism, including sugars and organic acids (as well as secondary metabolism, including phenolic compounds [ 23 ]), no studies have investigated these compounds in leaf tissues. According to the abovementioned outcomes, the present study showed that infection-specific responses of primary metabolites also occurred in the leaves.…”

“…Although PPV is one of the most-studied plant viruses, and there have been major advances in detection techniques, genome characterization and organization, gene expression and transmission, and the description of candidate genes involved in PPV resistance, information concerning the plant responses to PPV infection is very scarce [ 22 ]. Overall, most of the changes produced by PPV infection have been shown to be related to photosynthesis, antioxidant defense responses, and the primary and secondary metabolisms, but many features could influence these results, such as the Prunus species or cultivar, PPV strain, presence or absence of symptoms, type of tissue, and duration of infection [ 23 ]. A further aspect that would probably increase such divergences is represented by co-infection with other plum RNQP, which commonly occur in the field [ 12 ], but which have never been investigated from this point of view (to the best of our knowledge), even when occurring individually.…”