Comparative study of genome-wide plant biomass-degrading CAZymes in white rot, brown rot and soft rot fungi

Ayyappa Kumar Sista Kameshwar,Wensheng Qin

doi:10.1080/21501203.2017.1419296

Abstract

ABSTRACT We have conducted a genome-level comparative study of basidiomycetes wood-rotting fungi (white, brown and soft rot) to understand the total plant biomass (lignin, cellulose, hemicellulose and pectin) -degrading abilities. We have retrieved the genome-level annotations of well-known 14 white rot fungi, 15 brown rot fungi and 13 soft rot fungi. Based on the previous literature and the annotations obtained from CAZy (carbohydrate-active enzyme) database, we have separated the genome-wide CAZymes of the selected fungi into lignin-, cellulose-, hemicellulose- and pectin-degrading enzymes. Results obtained in our study reveal that white rot fungi, especially Pleurotus eryngii and Pleurotus ostreatus potentially possess high ligninolytic ability, and soft rot fungi, especially Botryosphaeria dothidea and Fusarium oxysporum sp., potentially possess high cellulolytic, hemicellulolytic and pectinolytic abilities. The total number of genes encoding for cytochrome P450 monooxygenases and metabolic processes were high in soft and white rot fungi. We have tentatively calculated the overall lignocellulolytic abilities among the selected wood-rotting fungi which suggests that white rot fungi possess higher lignin and soft rot fungi potentially possess higher cellulolytic, hemicellulolytic and pectinolytic abilities. This approach can be applied industrially to efficiently find lignocellulolytic and aromatic compound-degrading fungi based on their genomic abilities.

Highlights

Lignocellulose is degraded by a large group of fungi and bacteria (Daniel 2014)
Results obtained in our study reveal that white rot fungi, especially Pleurotus eryngii and Pleurotus ostreatus potentially possess high ligninolytic ability, and soft rot fungi, especially Botryosphaeria dothidea and Fusarium oxysporum sp., potentially possess high cellulolytic, hemicellulolytic and pectinolytic abilities
The total number of genes encoding for ligninolytic, cellulolytic, hemicellulolytic and pectinolytic enzymes calculated in this study reveals that white rot fungi are well equipped with efficient enzyme machinery for the degradation of lignin

Summary

Introduction

Lignocellulose is degraded by a large group of fungi and bacteria (Daniel 2014). Fungi have evolved progressively with their dominant degrading abilities to decay organic debris including plant biomass by penetrating through their hyphae and spores (for long-distance dispersal) (Kendrick 2001). Wood-rotting fungi are categorised into white, brown and soft rot fungi based on their growth substrate preferences and wood-decaying patterns (Kameshwar and Qin 2016a). White rot fungi exhibit excellent decaying abilities and are solely responsible for the degradation of lignin and polysaccharides in plant biomass. Microscopy-based studies have differentiated the white rot decay patterns morphologically into (a) simultaneous degradation of lignin and wood polysaccharides (e.g. Phanerochaete chrysosporium, Trametes versicolor, (b) selective degradation of plant biomass components (e.g. Phlebia radiata) (Rowell and Barbour 1989; Daniel 1994, 2014). Some fungi like Heterobasidium annosum exhibit both simultaneous and selective decay patterns (Daniel 2003)

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Results

Conclusion