Early Pathogen Recognition and Antioxidant System Activation Contributes to Actinidia arguta Tolerance Against Pseudomonas syringae Pathovars actinidiae and actinidifoliorum

• Published in: Frontiers in plant science Vol. 11; p. 1022
• Main Authors: Nunes da Silva, M., Vasconcelos, M. W., Gaspar, M., Balestra, G. M., Mazzaglia, A., Carvalho, Susana M. P.
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 22.07.2020
• Subjects: Actinidia chinensis; antioxidant system; gene expression; Plant Science; Pseudomonas syringae pv. actinidiae; Pseudomonas syringe pv. actinidifoliorum; susceptibility; susceptibility; antioxidant system; Pseudomonas syringe pv. actinidifoliorum; Actinidia chinensis; Pseudomonas syringae pv. actinidiae; gene expression
• ISSN: 1664-462X; 1664-462X
• DOI: 10.3389/fpls.2020.01022

and have distinct tolerances to pv. (Psa), but the reasons underlying the inter-specific variation remain unclear. This study aimed to integrate the metabolic and molecular responses of these two kiwifruit species against the highly pathogenic Psa and the less pathogenic pv. (Pfm) bacterial strains. Disease development was monitored weekly till 21 days post inoculation (dpi), analysing a broad number and variety of parameters including: colony forming units (CFU), foliar symptoms, total chlorophylls, lipid peroxidation, soluble polyphenols, lignin and defense-related gene expression. At the end of the experimental period inoculated with Psa presented the highest endophytic bacterial population, whereas inoculated with Pfm showed the lowest values, also resulting in a lower extent of leaf symptoms. Metabolic responses to infection were also more pronounced in with decreased total chlorophylls (up to 55%) and increased lipid peroxidation (up to 53%), compared with non-inoculated plants. Moreover, at 14 dpi soluble polyphenols and lignin concentrations were significantly higher (112 and 26%, respectively) in Psa-inoculated plants than in controls, while in no significant changes were observed in those metabolic responses, except for lignin concentration which was, in general, significantly higher in Psa-inoculated plants (by at least 22%), comparing with control and Pfm-inoculated plants. Genes encoding antioxidant enzymes ( , and ) were upregulated at an earlier stage in Psa-inoculated than in . In contrast, genes related with phenylpropanoids ( ) and ethylene ( ) pathways were downregulated in , but upregulated in in the later phases of infection. Expression of , responsible for pathogen recognition, occurred 2 dpi in , but only 14 dpi in . In conclusion, we found that is more tolerant to Psa and Pfm infection than and its primary and secondary metabolism is less impacted. higher tolerance seems to be related with early pathogen recognition, the activation of plant antioxidant system, and to the suppression of ET and JA pathways from an earlier moment after infection.