Chemical interactions between Verticillium longisporum and oilseed rape Brassica napus

by Husam Ibrahem Aroud
Doctoral thesis
Date of Examination:2013-07-03
Date of issue:2014-05-20
Advisor:Prof. Dr. Petr Karlovsky
Referee:Prof. Dr. Petr Karlovsky
Referee:Prof. Dr. Andreas von Tiedemann
Referee:Prof. Dr. Stefan Vidal
Persistent Address: http://dx.doi.org/10.53846/goediss-4508

 

 

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Abstract

English

Verticillium longisporum is a devastating vascular pathogen which infects plants from Brassicacae including oilseed rape Brassica napus, the pathogen infects the plant through the root and enters the vascular system to which it is confined for most of its biotrophic part of life cycle. Bio-chemical interactions between the pathogen and the plants occur in the xylem vessels and specifically in the xylem sap. Small molecules in the xylem sap of oilseed rape Brassica napus are the topic of the two parts of this study. In the first chapter, isolation and purification of secondary metabolites which specifically occur in the xylem sap of V. longisporum-infected B. napus are described. By using a preparative HPLC system based on the analytical HPLC which detected these secondary metabolites, one of these secondary metabolites which has the exact mass of 612.1197 Da obtained. This compound was previously detected in positive and negative modes of ionization m/z 613 [M+H]+, m/z 611 [M-H]-, respectively. The purified amount of the compound was not sufficient for complete structure elucidation. In the second chapter, a bio-assay was developed to study the inhibition effect of the small molecules present in xylem sap of V.longisporum infected B. napus plants on two microorganisms, the bacterium Agrobacterium tumefaciens and the yeast Saccharomyces sereviciae. An inhibition effect was observed on A.tumifaciens but not on S. cervesiae when the entire xylem sap of B. napus was used. The inhibition effect was negligible after removing the large molecules which have molecular weight larger than 3000 Da; therefore, small molecules in xylem sap have no or a negligible inhibition effect on A. tumifaciens. In the third chapter, comparative metabolic profiling of supernatant of wild type V. longisporum grown on Potato dextrose broth (PDB) medium was compared to mutant type resulted from silencing Vl-PKS-1, a gene encode to polyketide synthase in V. longisporum. The study was conducted using chemical analytical techniques (HPLC combined with mass spectrometry (MS), Diode array detection (DAD),UV Time-of-flight mass spectrometry (TOFMS.) As a result, several metabolites were found in the supernatant of V. longisporum wild type strain which were not present or present in lower amounts in the supernatant of Vl-PKS-1 silenced type.
Keywords: Verticillium longisporum; Brassica napus; Secondary metabolites; Xylem sap
 
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