Implementation of genetic and untargeted metabolomics to study the role of the terpene synthase vir4 from Trichoderma virens in plant-microbe interactions : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University

Trichoderma virens actively interacts with plants roots in natural and agricultural ecosystems. Its ability to persist in the rhizosphere and to internally colonise plants roots is driven among others by the production of a wide diversity of specialised metabolites that encompass a complex bouquet of volatile organic compounds (VOCs), mostly comprising volatile terpenes. Terpenes are abundantly produced natural products with several biological properties. However, little is known about the role of T. virens volatile terpenes as signalling mediators of the inter-colony communication and modulators of the plant-symbiont crosstalk. In this study, the process by which T. virens volatile terpenes modulate fungal development was examined by the generation of a terpene synthase (vir4) deletion mutant and its functional characterisation. In T. virens, the deletion of vir4 altered a) the emission of volatile terpenes and C8 compounds, b) fungal development (fungal growth, conidiation, germination and colony morphology, pigmentation and hydrophobicity) and, c) modulated the non-volatile fungal metabolome. Using Zea mays as an agriculturally relevant plant model, the role of T. virens volatile terpenes as facilitators of roots colonisation, growth promotion, and phytometabolome modulators was assessed by comparing the T. virens vir4 null mutant with its parental strain. To achieve this, a combination of confocal microscopy, endophytism, growth promotion bioassays and untargeted metabolomics of the plant-microbe interaction were performed. Confocal microscopy and endophytism bioassays revealed that the ability of T. virens to penetrate, colonise, and persist in the host plant does not depend on vir4-associated VOCs. Attempts to assess the relationship between T. virens volatile terpenes and maize growth promotion were carried out in sterile soil conditions, but no growth promotion occurred. Untargeted metabolomics of roots and leaves during the T. virens-maize interaction allowed the detection of metabolic features characteristic of the symbiotic interaction. Intensities in flavonoids, nitrogen-containing specialised metabolites, lipids, and organic acids were modulated by fungal colonisation. Several, yet unidentified, maize metabolic features were specifically modulated by T. virens vir4 colonisation, demonstrating that untargeted metabolomics is a suitable tool to describe dynamic metabolic patterns in plant-beneficial microbe interactions. In summary, these results indicate that T. virens vir4-associated VOCs regulate fungal development and modulate the phytometabolome of the host.

Grantor dc:publisher

Lincoln University

Year dc:date

2019

Author dc:creator

• Padilla Arizmendi, Fabiola

• Trichoderma virens
• volatile organic compounds
• terpenes
• terpene synthases
• plant-microbe interactions
• beneficial microorganisms
• root colonisation
• maize
• plant metabolism
• ANZSRC::060702 Plant Cell and Molecular Biology
• ANZSRC::060705 Plant Physiology
• ANZSRC::060504 Microbial Ecology

Licence

• https://researcharchive.lincoln.ac.nz/pages/rights

Language dc:language

en

Identifier

Q112949801

OAI identifier oai:identifier

oai:researcharchive.lincoln.ac.nz:10182/11699