Mapping grapevine metabolites in response to pathogen challenge: a Mass Spectrometry Imaging approach

Every year, viticulture is facing several outbreaks caused by established diseases, such as downy mildew and grey mould, which possess different life cycles and modes of infection. To cope with these different aggressors, grapevine must recognize them and arm itself with an arsenal of defense strategies.

The regulation of secondary metabolites is one of the first reactions of plants upon pathogen challenge. Their rapid biosynthesis can highly contribute to strengthen the defense mechanisms allowing the plant to adapt, defend and survive. Most of the works published so far, have focused on untargeted and/or targeted metabolite accumulations in a sample pool of an infected tissue. However, with these approaches it is not possible to obtain knowledge about the actual localization of the accumulated metabolites nor their specific sites of action.

Mass spectrometry imaging (MSI) analytical techniques enable to visualize and map the spatial distribution of metabolites within plant tissues allowing to a better understanding of metabolite biosynthesis, localization and functions^[1].

We have studied the spatial distribution of different metabolites in grapevine leaves infected with different pathogens, using Matrix Assisted Laser Desorption Ionization-MSI. Our results demonstrated that in grapevine-P. viticola interaction, putatively identified sucrose presented a higher accumulation mainly in the veins of the leaves, leading to the hypothesis that sucrose metabolism is being manipulated by the development structures of P. viticola^[2]. Also, in grapevine leaves infected with B. cinerea, our results show that putatively identified stilbene phytoalexins accumulate in areas close to infection sites, with a high molecular diversity as evidenced by the detection of various oligomeric forms^[3].

Our work opens new doors for the scientific community to gain a comprehensive understanding of the dynamics and variations of metabolite profiles in grapevine organs, at different developmental stages and under various stress conditions. This knowledge is crucial for elucidating the role of specific metabolites in grapevine defense mechanisms, identify specific regions of high or low metabolite production, which can contribute to targeted breeding to enhance disease resistance traits and impact grapevine productivity and quality.

Acknowledgements: Work funded by FCT-Portugal – research contract 2022.07433.CEECIND.

References:

1. Maia M. et al. (2022). Molecular Localization of Phytoalexins at the Micron Scale: Towards a Better Understanding of Plant-Phytoalexin-Pathogen Dynamics. J. Agric. Food Chem. 70, 30, 9243–9245, DOI 10.1021/acs.jafc.2c04208
2. Maia M. et al. (2022) Grapevine Leaf MALDI-MS Imaging Reveals the Localisation of a Putatively Identified Sucrose Metabolite Associated to Plasmopara Viticola Front. Plant Sci. 13:1012636, DOI 10.3389/fpls.2022.1012636
3. Maia M. et al. (Submitted) Profiling and localization of stilbene phytoalexins revealed by MALDI-MSI during the grapevine-Botrytis cinerea J. Agric. Food Chem.