Genomic Analysis and Assessment of Melanin Synthesis in Amorphotheca resinae KUC3009.

Jeong-Joo Oh,Sun Lul Kwon,Jee Young Kim,Gyu-Hyeok Kim,Young Jun Kim,Changsu Lee,Jung Woo Kim,Myeong-Eun Lee

doi:10.3390/jof7040289

Abstract

This study reports the draft genome of Amorphotheca resinae KUC30009, a fungal isolate with promising industrial-scale melanin production potential. The mechanisms for melanin or melanin-related pigment formation of this strain were examined through bioinformatic and biochemical strategies. The 30.11 Mb genome of A. resinae contains 9638 predicted genes. Genomic-based discovery analyses identified 14 biosynthetic gene clusters (BGCs) associated with secondary metabolite production. Moreover, genes encoding a specific type 1 polyketide synthase and 4-hydroxynaphthalene reductase were identified and predicted to produce intermediate metabolites of dihydroxy naphthalene (DHN)-melanin biosynthesis pathway, but not to DHN-melanin. These findings were further supported by the detection of increased flaviolin concentrations in mycelia and almost unchanged morphologies of the culture grown with tricyclazole. Apart from this, the formation of melanin in the culture filtrate appeared to depend on the laccase-like activity of multi-copper oxidases. Simultaneously, concentrations of nitrogen-containing sources decreased when the melanin formed in the media. Interestingly, melanin formation in the culture fluid was proportional to laccase-like activity. Based on these findings, we proposed novel strategies for the enhancement of melanin production in culture filtrates. Therefore, our study established a theoretical and methodological basis for synthesizing pigments from fungal isolates using genomic- and biochemical-based approaches.

Highlights

Contrary to their synthetic counterparts, the demand for natural pigments has been steadily increasing in recent years in response to global market shifts and consumer preferences [1,2]
A previous study reported that A. resinae strain KUC3009 cultures cause discoloration of chromated copper arsenate-treated wood [32]
We previously reported that A. resinae KUC3009 produced considerable amounts of melanin in the culture filtrate

Summary

Introduction

Contrary to their synthetic counterparts, the demand for natural pigments has been steadily increasing in recent years in response to global market shifts and consumer preferences [1,2]. Filamentous fungi have been gaining recognition as a potential microbial source of natural pigments; the industrial applications of these microorganisms are not as widespread as those involving algae or bacteria [3]. Fungal pigments are secondary metabolites, and most of their synthesis pathways and optimal production conditions remain largely unknown [10], which limits their optimization and widespread adoption in industrial applications. With the accumulation of high-throughput sequencing data, bioinformatics tools can be used to identify putative genes or gene clusters involved in metabolite production. Comprehensive prediction of the provisional biosynthetic pathways of pigments would be possible based on the identified putative genes or gene clusters [11]. Genomic studies could provide fundamental insights into the pathways associated with secondary metabolite synthesis in fungi, paving the way for their adoption in industrial-scale processes. We previously reported the promising capacity of the fungus Amorphotheca resinae

Methods

Results

Conclusion