Phytotoxic metabolites produced by Verticillium dahliae Kleb. in olive wilting: a chemical and spectroscopic approach for their molecular characterisation

Abstract

Most of the symptoms associated with Verticillium wilt disease in olive cultivation are due to complexes excreted by Verticillium dahliae. In this study chemical and physico-chemical techniques were combined to investigate how the molecular structure of phytotoxins isolated from two pathotypes of Verticillium dahliae, defoliating, D, and non-defoliating, ND, grown on two different media, Verticillium-dahliae-Medium (VdM) and Simulated Xylem-fluid-Medium (SXM), can affect their aggressiveness. Data obtained highlight important structural differences, both in term of elemental composition and in functional groups distribution. Such peculiarities strongly affect their solubility, resulted higher for the phytotoxins from D pathotype. This property likely induces serious modifications of the conformational state of the proteinaceous component, making tyrosine residues accessible to the phosphate ion. A phosphorylation mechanism would thus be promoted, that is going to interfere with the function of the involved proteins in intracellular signalling networks, likely by altering its role in modulating the plant’s response.

Graphical Abstract

Keywords:

• : Verticillium dahliae Kleb.
• phytotoxicity
• elemental composition
• Fourier transform infrared
• fluorescence spectroscopies

Acknowledgements

Grateful thanks are expressed to Mr. L. Scarola for his technical support during the bioassay.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was in part financially supported by the project “Meccanismi di resistenza alla verticilliosi e caratterizzazione di varietà meridionali di olivo” granted by Fondazione Cassa di Risparmio di Puglia (Apulia, Italy) year 2010.