Terrein Biosynthesis in Aspergillus terreus and Its Impact on Phytotoxicity

Christoph Zaehle,Markus Gressler,Ekaterina Shelest,Elena Geib,Christian Hertweck,Matthias Brock

doi:10.1016/j.chembiol.2014.03.010

Christoph Zaehle, Markus Gressler + Show 4 more

Open Access

https://doi.org/10.1016/j.chembiol.2014.03.010

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Abstract

Terrein is a fungal metabolite with ecological, antimicrobial, antiproliferative, and antioxidative activities. Although it is produced by Aspergillus terreus as oneof its major secondary metabolites, not much isknown 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, and6,7-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.

Highlights

Aspergillus terreus is a ubiquitous filamentous fungus frequently isolated from soil rhizospheres (He et al, 2004; Wijeratne et al, 2003), decaying organic matter (Reddy and Singh, 2002), and marine environments (Damare et al, 2006)
Several gene clusters in A. terreus responsible for metabolite production have been analyzed, including lovastatin (Hendrickson et al, 1999), methylsalicylic acid (Fujii et al, 1996), atrochrysone (Awakawa et al, 2009), acetylaranotin (Guo et al, 2013), and terretonin (Guo et al, 2012), as well as the gene cluster for the PKS-NRPS hybrid metabolite isoflavipucine/dihydroisoflavipucine (Gressler et al, 2011). The latter belongs to the family of fruit rot toxins, implying that A. terreus could have adapted to the decay of plant organic matter
We report the serendipitous discovery of the terrein biosynthesis gene locus while searching for polyketide synthases that might be responsible for the pigmentation of A. terreus conidia

Summary

Introduction

Aspergillus terreus is a ubiquitous filamentous fungus frequently isolated from soil rhizospheres (He et al, 2004; Wijeratne et al, 2003), decaying organic matter (Reddy and Singh, 2002), and marine environments (Damare et al, 2006). Several gene clusters in A. terreus responsible for metabolite production have been analyzed, including lovastatin (Hendrickson et al, 1999), methylsalicylic acid (Fujii et al, 1996), atrochrysone (Awakawa et al, 2009), acetylaranotin (Guo et al, 2013), and terretonin (Guo et al, 2012), as well as the gene cluster for the PKS-NRPS hybrid metabolite isoflavipucine/dihydroisoflavipucine (Gressler et al, 2011) The latter belongs to the family of fruit rot toxins, implying that A. terreus could have adapted to the decay of plant organic matter

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Discussion

Conclusion