Diversity and evolution of terpene synthase genes in Ascomycota

Abstract

Terpene synthase (TPS) genes encode for terpenoids. These enzymes are secondary metabolites with various functions in fungi, such as defense against predators. They are also used in various industries, including the baking, cosmetic, and farming sectors. Despite their biological and industrial importance, little is known about their distribution and evolution in the fungal lineage Ascomycota. The research presented in this dissertation, therefore, investigated their distribution and the evolutionary mechanisms involved in these fungi. The first chapter of this dissertation reviewed the current body of literature regarding the characteristics of TPS genes and their terpenoid enzymes. It also considered the biological roles of these enzymes in fungi and their industrial applications. Finally, the review reflected on bioinformatics methods for analysing TPS genes. Two research chapters then followed the review chapter. Results from the research in these chapters showed that Ascomycota species harbour TPS genes that vary in copy number and type, ranging from two to 56 copies. The type of terpenoids that were identified included prenyltransferase (PT), terpene cyclase (TC) (predominantly sesquiterpenes and diterpenes). Results from the last chapter showed that this variation is due to duplication, gene loss, and horizontal gene transfer (HGT). Ancestral character state reconstruction of the TPS orthologous groups showed that the ancestor of Ascomycota had only three orthologous groups, and the number of orthologous groups expanded and contracted throughout the evolution of the ancestors of extant species.