Terrein Biosynthesis in Aspergillus terreus and Its Impact on Phytotoxicity

Abstract

Terrein is a fungal metabolite with ecological, antimicrobial, antiproliferative, and antioxidative activities. Although it is produced by Aspergillus terreus as one of its major secondary metabolites, not much is known about its biosynthetic pathway. Here, we describe an unexpected discovery of the terrein biosynthesis gene locus made while we were looking for a PKS gene involved in production of conidia coloration pigments common for Aspergilli. The gene, ATEG_00145, here named terA, is essential for terrein biosynthesis and heterologous production of TerA in Aspergillus niger revealed an unusual plasticity in the products formed, yielding a mixture of 4-hydroxy-6-methylpyranone, orsellinic acid, and 6,7-dihydroxymellein. Biochemical and molecular genetic analyses indicate a low extension cycle specificity of TerA. Furthermore, 6-hydroxymellein was identified as a key intermediate in terrein biosynthesis. We find that terrein production is highly induced on plant-derived media, that terrein has phytotoxic activity on plant growth, and induces lesions on fruit surfaces.

Fungal biosynthesis of the bibenzoquinone oosporein to evade insect immunity

“…Based on previous reports that OA can be converted into oosporein by B. bassiana (8) and that OA is biosynthesized by PKSs in fungi (22,23), we performed a genome-wide modulation analysis of 12 PKSs encoded in the Beauveria genome (SI Appendix, Fig. S1A).…”

“…S2) produces a mixture of OA, 4-hydroxy-6-methylpyranone, and 6,7-dihydroxymellein. The latter is further oxidized to terrein by monooxygenase and multicopper oxidase (23). The OA produced by PKS ArmB is esterified to a diverse class of sesquiterpene alcohols in the plant pathogen Armillaria mellea (32).…”

“…wrote the paper. modules with the OrSA of Aspergillus nidulans (22), TerA of Aspergillus terreus (23), and FgPKS14 of Fusarium graminearum (24), which have been verified to produce OA (SI Appendix, Fig. S1B).…”

“…Biologically, however, an early experiment demonstrated that 14 C-labeled orsellinic acid (OA) (2) could be converted to bibenzoquinone oosporein in B. bassiana cultures (8). It is now clear that OA can be biosynthesized by PKSs in bacteria (21) and fungi (22)(23)(24). These findings suggest that oosporein may be biosynthesized through OA by a PKS gene cluster in Beauveria.…”

When green and red mycology meet: Impressions from an interdisciplinary forum on virulence mechanisms of phyto- and human-pathogenic fungi

“…He described the interplay of A. terreus with banana tissue as mediated by the action of a fruit rot toxin that is further supported by the phytotoxin terrein. 19 From expression analyses, regulatory mechanisms that go beyond primary metabolism were identified, demonstrating an intertwined relationship between global regulators and gene cluster-specific transcription factors in this fungal pathogen of plants and humans. 20 J€ org K€ amper from the Karlsruhe Institute of Technology in Germany presented his recent insights on pathogenic development of Ustilago maydis in planta that is regulated by two transcription factors, Biz1 and Hdp2, identified by their relationship to the b mating-type locus-dependent class I gene rbf1.…”