Incidence and characterisation of mycoviruses from Aspergillus fumigatus
Author(s)
Jamal, Atif
Type
Thesis
Abstract
This study investigated the incidence and characterisation of mycoviruses in a range of different fungi including Phytophthora spp. Phlebiopsis gigantea and Aspergillus fumigatus and their effects on their hosts. The investigation developed methodology for rapid molecular characterisation of dsRNA elements from different fungi which were applied in detail to a range of isolates of A. fumigatus. DsRNA elements or mycoviruses are present in almost all major classes of fungi where they lack an extracellular phase and are transmitted intracellulary via anastomosis or spores. Mycoviruses can confer a range of phenotypes on their fungal hosts ranging from symptomless to debilitating and hypovirulence to hypervirulence. In most cases most fungal mycovirus infections are symptomless and the effects of A. fumigatus mycoviruses on fitness and growth of infected isolates were also investigated. A screen of thirty nine clinical isolates of A. fumigatus, which is an opportunistic human pathogen and causes aspergillosis in immunocompromised patients, revealed the presence of dsRNA elements which were hitherto unknown. Two mycoviruses were identified including a chrysovirus (isolate A-56) and an unclassified, triripartite dsRNA-containing mycovirus (isolate A-54). All four dsRNA segments of the A-56 chrysovirus were sequenced in their entirety using the methodologies developed earlier in the investigation and the sequences analysed and compared to other members of the family Chrysoviridae and other characterised mycovirus families. Also the effects of the chrysovirus on the fitness of the host fungus were studied as was transfer of the purified chrysovirus to cured strains of A. fumigatus via protoplast fusion and direct transfection by different methods. It is intended to develop the use of dsRNA elements for gene silencing in A. fumigatus and towards this aim a full-length clone of the smallest A-56 dsRNA has been constructed and characterised and used to produce dsRNA transcripts for infection and amplification in the fungus.
Date Issued
2010
Date Awarded
2010-11
Advisor
Coutts, Robert
Sponsor
Higher Education Commission of Pakistan
Creator
Jamal, Atif
Publisher Department
Life Sciences: Division of Biology
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)