Abstract
The Oomycete Plasmopara viticola is responsible for downy mildew, which is one of the most damaging grapevine diseases. Due to the strictly biotrophic way of life of P. viticola, its metabolome is relatively poorly characterized. In this work, we have used a mass spectrometry-based non-targeted metabolomic approach to identify potential Plasmopara-specific metabolites. This has led to the characterization and structural elucidation of compounds belonging to three families of atypical lipids, which are not detected in healthy grapevine tissues. These lipids include ceramides and derivatives of arachidonic and eicosapentaenoic acid, most of which had not been previously described in Oomycetes. Furthermore, we show that these lipids can be detected in Plasmopara-infected tissues at very early stages of the infection process, long before the appearance the first visible symptoms of the disease. Therefore, the potential use of these specific lipids as markers to monitor the development of P. viticola is discussed.
Highlights
Plasmopara viticola is an obligate biotrophic Oomycete responsible for downy mildew, which is one of the most damaging grapevine diseases
Both eicosapentaenoic acid (EPA) and arachidonic acid (AA) had previously been identified in mycelial extracts of Phytophthora infestans, another phytopathogenic Oomycete causing the late blight of potato (Bostock et al, 1981)
Commercial EPA and AA standards were analyzed by UHPLC-HRMS using the same conditions as those used for P. viticola extracts
Summary
Plasmopara viticola is an obligate biotrophic Oomycete responsible for downy mildew, which is one of the most damaging grapevine diseases. Grapevine responses to downy mildew infection have been characterized in both compatible and incompatible situations, through the study of susceptible Vitis vinifera cultivars and resistant species such as Vitis riparia, V. rupestris, or Muscadinia rotundifolia. Metabolomic profiling experiments have revealed profound changes in grapevine tissues upon downy mildew infection, which affect both the primary and the secondary metabolism (Figueiredo et al, 2008; Ali et al, 2009; Buonassisi et al, 2017). One of the most prominent metabolic change is the biosynthesis of large amounts of stilbene phytoalexins
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