Sugars and organic acids in plum fruit affected by Plum pox virus

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

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.

Identification of Somatosensory Compounds Contributing to Slipperiness and Thickness Perceptions in Canned Prunes (Prunus domestica)

The role of small molecules on the somatosensory properties of prunes (Prunus domestica) was investigated. Sensory descriptive analysis defined two main somatosensations, "thickness" and "slippery". On the basis of these two attributes, sensory-guided multidimensional fractionation techniques allowed for the isolation of four main compounds, which were identified by mass spectrometry and comparison to authentic standards. Three compounds were identified as monosubstituted isomers of chlorogenic acid, namely, 1-O-caffeoylquinic acid (1-CQA), 3-O-caffeoylquinic acid (3-CQA), and 4-O-caffeoylquinic acid (4-CQA), in addition to a fourth, vanillic acid glucoside (VG). Sensory recombination model analysis of each compound at endogenous concentrations of the prunes indicated that all compounds significantly contributed to slippery sensations, whereas 3-CQA, 4-CQA, and VG contributed to thickness sensations (α = 0.05).

Dynamic changes impact the plum pox virus population structure during leaf and bud development

Plum pox virus (PPV) is a worldwide threat to stone fruit production. Its woody perennial hosts provide a dynamic environment for virus evolution over multiple growing seasons. To investigate the impact seasonal host development plays in PPV population structure, next generation sequencing of ribosome associated viral genomes, termed translatome, was used to assess PPV variants derived from phloem or whole leaf tissues over a range of plum leaf and bud developmental stages. Results show that translatome PPV variants occur at proportionately higher levels in bud and newly developing leaf tissues that have low infection levels while more mature tissues with high infection levels display proportionately lower numbers of viral variants. Additional variant analysis identified distinct groups based on population frequency as well as sets of phloem and whole tissue specific variants. Combined, these results indicate PPV population dynamics are impacted by the tissue type and developmental stage of their host.

Multilocation comparison of fruit composition for 'HoneySweet', an RNAi based plum pox virus resistant plum

'HoneySweet', a transgenic plum (Prunus domestica) resistant to plum pox virus through RNAi, was deregulated in the U.S. in 2011. The compositional study of 'HoneySweet' fruit was expanded to include locations outside of the US as well as utilizing a wide variety of comparators and different collection years to see the variability possible. The results revealed that plums have a wide variation in composition and that variation among locations was greater than variation among cultivars. This was also the case for different years at one location. The results supported the supposition that the transgene and insertion event had no significant effect on the composition of 'HoneySweet' fruit even under virus pressure, and that it fell in the normal range of composition of commercially grown plums. It also suggested that the effect of environment is as great as that of genetics on the fruit composition of plums.