(149e) Rnaseq Reveals Substrate-Specific Lignocellulosic Degradation Responses in Anaerobic Gut Fungi

Complex microbiomes within the digestive tract of herbivores are increasingly of interest for the discovery of novel lignocellulose degrading enzymes for the production of biofuels.  Anaerobic fungi, in particular, are prolific digesters of crude lignocellulose through a combination of powerful secreted enzymes and invasive growth.  However, due to difficulties associated with their isolation and study, very little is known about these enzymes.  Here, we pursued a systems level strategy integrating transcriptomics and phenotypic studies to probe the hydrolytic capabilities of these unusual microbes in detail for the first time.  Using a novel isolate of the Piromyces genus, we have assembled the first de novo strand specific gut fungal transcriptome with RNAseq revealing a complex landscape containing hundreds of novel biomass degrading enzymes and regulatory antisense transcripts.  Many of these transcripts are strongly repressed by simple sugars and co-regulated within functional regulons of coordinated gene expression.  Gene Set Enrichment Analysis also revealed a tunable hydrolytic response that was specific to each cellulosic substrate and core enzymes that are believed to be integral to substrate recognition and the induction of this response.  Highly conserved fungal transcription factors from Aspergillus that may mediate this behavior were also identified.  Our work captured a previously unelucidated layer of gut fungal regulation, provides a roadmap for future platform engineering efforts and illuminates successful natural strategies for the formulation of industrial cellulase cocktails.