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Enhanced biocontrol options for the Australian sugar industry: a proteomic approach

thesis
posted on 28.03.2022, 02:30 authored by Nirupama Shoby Manalil
The filamentous fungus Metarhizium anisopliae is a naturally occurring biological control agent of many insects including the greyback canegrub (Dermolepida albohirtum), a sugarcane pest in Australia. While there have been some gene-based approaches into identifying determinants for biological control and developing improved strains, this study provides a new comparative proteomics approach into identifying key proteins produced by M. anisopliae during infection of greyback canegrubs. Pathogenicity-related proteins have been identified by both liquid and solid culture approaches using proteomic technologies. Proteome maps of healthy canegrubs, canegrubs infected with Metarhizium and fungus only were produced and analysed. Comparative proteome analysis of proteins produced in solid culture provided a view into cellular reactions triggered in the canegrub in response to Metarhizium infection. Some of the proteins identified included cytoskeleton proteins, proteases, peptidases, metalloproteins and proteins involved in signal transduction. Liquid culture approach was used to display secreted proteins of Metarhizium growing on the whole greyback canegrubs and their isolated cuticles. Proteins identified included 64-kDa serine carboxypeptidase, 1,3 β-exoglucanase, dynamin GTPase, THZ kinase, calcineurin like phosphoesterase and phosphatidylinositol kinase. These proteins have not been previously identified from the culture supernatant of M. anisopliae during infection. To our knowledge, this is the first proteomic map established to study the extracellular proteins secreted by M. ansiopliae (FI-1045), a strain currently used for biological control of greyback canegrubs. Metarhizium anisopliae strain FI-1045 was further subjected to UV mutagenesis to select mutants that can tolerate better environmental conditions such as varying temperature and pH ranges. M. anisopliae mutant strain (NM10) was isolated and bioassays against greyback canegrubs proved that the mutant strain was more virulent than the parental strain. Two-dimensional electrophoresis was employed to display secreted proteins of the M. anisopliae mutant strain (NM10) growing on the whole greyback canegrubs and their isolated cuticles, in order to identify various proteins involved in infection of canegrubs. Eighty six secreted proteins were identified in this approach, amongst them six proteins that have not been previously identified from the culture supernatant of M. anisopliae during infection. These included the 56-kDa aspartyl aminopeptidase, 29-kDa secreted aspartyl protease, cyclin-dependent protein kinase, thymidylate kinase, septin and adenylate kinase. Finally, mutant strain NM10, generated by UV-mutagenesis was stably transformed and found to be highly resistant to benomyl, a commonly used fungicide in agriculture. Benomyl resistant transformants were found to tolerate 40 times higher concentration of benomyl than then amount that inhibits the parental strain. Laboratory bioassays proved that four transformants resistant to benomyl retained virulence characteristics against greyback canegrubs. The proteomic methods established, developed and applied in this thesis proved their strength and suitability in the visualisation, detection and identification of proteins produced by the fungus during infection of greyback canegrubs. Genetic manipulation techniques such as mutagenesis and transformation methods described in this thesis demonstrated successful steps in improving the Metarhizium strain while retaining pathogenicity against the greyback canegrubs. Combining the proteomics data obtained in this work with other "omics‟ data such as genomics, transcriptomics, metabolomics and bioinformatics, will lead to a more complete understanding of the biology of canegrub infection by Metarhizium at the molecular level.

History

Table of Contents

1. General introduction -- 1.2 The entomopathogenic Sordariomycete Metarhizium anisopliae -- 1.3 Canegrubs and the Australian sugar industry -- 1.4 Prospects of exploiting entomopathogenic fungi as biocontrol agents -- 1.5 Genetic engineering improved strains of entomopathogenic fungi -- 1.6 Microbial proteomics -- 1.7 Types of proteomics -- 1.8 Two-dimensional electrophoresis (2-DE) -- 1.9 Literature cited -- 1.10 Aims of the thesis -- 2. Proteomic map of the greyback canegrub, Dermolepida albohirtum (Waterhouse) - Manuscript I -- 3. A proteomic view into infection of greyback canegrubs (Dermolepida albohirtum) by Metarhizium aniopliae - Manuscript II -- 4. Comparative analysis of the Metarhizium anisopliae secretome in response to the greyback canegrubs and grub cuticles - Manuscript III -- 5. A mutant strain of Metarhizium anisopliae var. anisopliae with increased virulence against greyback canegrubs -- 6. Proteomic analysis of the secretome of Metarhizium anisopliae in response to exposure to the greyback canegrubs and grub cuticles - Manuscript IV -- 7. Biolistic transformation of the entomopathogenic fungus Metarhizium anisopliae to high resistance to benomyl -- 8. Summary of main findings and conclusions -- 8.1 References -- 9. Future work

Notes

"A thesis submitted in fulfillment of the requirements for the degree of Doctor of Philosophy" Includes bibliographical references Thesis by publication. "November 2009" Typescript.

Awarding Institution

Macquarie University

Degree Type

Thesis PhD

Degree

Thesis (PhD), Macquarie University, Faculty of Science, Dept. of Chemistry and Biomolecular Sciences

Department, Centre or School

Department of Chemistry and Biomolecular Sciences

Year of Award

2010

Principal Supervisor

Helena Nevalainen

Additional Supervisor 1

Valentino (Junior) Te'o

Rights

Copyright Nirupama Shoby Manalil 2010. Copyright disclaimer: http://mq.edu.au/library/copyright Access to this thesis is restricted to Macquarie University staff and students. Staff and students of Macquarie University should contact researchonline@mq.edu.au to organise access.

Language

English

Extent

1 online resource (221 leaves, bound) ill. (some col.)

Former Identifiers

mq:71731 http://hdl.handle.net/1959.14/1277511