Characterisation of secondary metabolite pathways in the Ceratocystidaceae

Abstract

Members of Ceratocystistidaceae (phylum Ascomycota, class Sordariomycetes) include fungal pathogens that cause diseases on a broad spectrum of hosts, leading to substantial economic losses globally. The objective of this thesis was to provide insights into the secondary metabolite pathways of this family. For this purpose, we used whole genome sequences of 23 different members of Ceratocystistidaceae. Our results showed that all of the genomes contained putative clusters containing a reducing and non-reducing type I PKS as well as a type III PKS. Phylogenetic analyses of non-reducing-PKS-I and also PKS-III suggested that these genes were already present in the ancestor of the Ceratocystidaceae. By contrast, the various reducing type I PKS-containing clusters identified in these genomes, appeared to have distinct origins during the evolution of this family. Although one of the identified clusters potentially allows for the production of melanin, their functional characterization will undoubtedly reveal many novel and important compounds implicated in the biology of the Ceratocystidaceae. We have also found two highly conserved nonribosomal peptide synthetase genes in all genomes of Ceratocystidaceae and their potential products were predicted. These findings help to better understanding of the diversity and evolution of NRPS biosynthesis pathways in this family. We further, optimized an Agrobacterium mediated transformation system for Ceratocystis. This will allow for the functional characterization of the genes and genetic elements underlying the biological properties of this important fungus and its relatives. The average ergosterol content of different genera of Ceratocystidaceae was different from each other. We also identified all possible terpenoid related genes and biosynthetic clusters in all genomes used in this study. We found a highly conserved terpenoid gene cluster containing some of the ergosterol biosynthetic genes in all genomes. An additional terpenoid gene cluster was also identified in all the Ceratocystidaceae with geranylgeranyl pyrophosphate as a core gene, which could be involve in diterpenoid production. The outcomes of this thesis shed light on our knowledge of secondary metabolite biosynthesis pathways in Ceratocystidaceae.