Computational and molecular study of terpene synthase genes in trichoderma

  1. Isabel Vicente Muñoz
Supervised by:
  1. Enrique Monte Vázquez Director
  2. Giovanni Vannacci Director

Defence university: Universidad de Salamanca

Year of defence: 2020

  1. Christophe Clément Chair
  2. Lorenzo Guglielminetti Secretary
  3. María Rosa Hermosa Prieto Committee member

Type: Thesis


Trichoderma is a fungal genus comprising a large number of species of great interest for plant protection and industry. The broad spectrum of lifestyles of the isolates belonging to this genus is likely supported by the diversity of their Secondary Metabolites (SMs) arsenal. In the present work, we combined genome mining and comparative genomic approaches to provide an extensive view of the SMs potential in this genus. Assessment of the core-genes and Biosynthetic Gene Clusters (BGCs) involved in SMs biosynthesis in the genomes of 21 isolates of 17 Trichoderma species showed that closest phylogenetic species tend to have similar SMs inventories, while lifestyle diversity could explain differences found among clades. Trichoderma contains a striking number of terpenoid synthases (TSs) genes, whose almost half is included in clusters. Characterization based on conserved sequence features and phylogenetic analysis with known TS proteins revealed the putative functions of 15 groups of prenyl transferases, terpene cyclases and chimeric proteins, providing an overview of the diversity of these enzymes in the genus. Trichodiene synthases (TRI5)-encoding genes were found in different genomic contexts in the non-trichothecene producer species. In particular, tri5 genes from T. gamsii isolates are embedded in a 21.3 Kb putative cluster including a transcription factor, some tailoring enzymes and a transporter. Since T. gamsii lacks the other TRI genes required for trichothecene production, we hypothesize that tri5 might be involved, in this species, in the biosynthesis of sesquiterpene/s other than trichothecenes, therefore participating in not yet defined metabolic pathways in Trichoderma. The characteristics of the isolate T6085 of T. gamsii (Tgam), known both to antagonize Fusarium spp. and to reduce Fusarium Head Blight (FHB) on wheat, and for its ability to colonize the rhizosphere and, endophytically, the wheat roots, enabled to study the regulation of the TS genes in different environments. Overall, oxidative and saline stresses, N starving, and availability of C source differentially affected TS genes expression, and results suggest that production of indole diterpenes could occur in response to oxidative stress. TS genes expression did not change significantly when the fungus was growing on wheat spikes in presence/absence of F. graminearum. In contrast, an evident reprogramming of terpene biosynthesis seems to take place when the fungus colonizes the roots (on PDA) compared to when it grows on PDA alone. Specifically, if we consider the expression of tri5, results suggest this gene in T. gamsii has a different type of regulation compared to what is known for tri5 of T. brevicompactum. The strong up-regulation of tri5 found when the fungus colonizes the wheat roots suggests this gene could have an important role in the interaction with the plant. In addition, metabolic profiles of Tgam revealed the absence of trichothecene compounds, and the ability of the fungus to produce diterpenes and high amounts of pyrones. In summary, we provide i) an extensive view of the SMs potential in Trichoderma, ii) a genomic characterization of the TS inventory in the genus, iii) a picture of TS gene regulation in Tgam in different environments, iv) a step forward to deciphering the regulation of tri5 in Tgam and its relevance in the relation with the plant, and v) interesting questions about the biological significance of tri5 in beneficious Trichoderma species.