Transcriptome Sequencing and Comparative Analysis of Piptoporus betulinus in Response to Birch Sawdust Induction

Evolution of substrate-specific gene expression and RNA editing in brown rot wood-decaying fungi

Fungi that decay wood have characteristic associations with certain tree species, but the mechanistic bases for these associations are poorly understood. We studied substrate-specific gene expression and RNA editing in six species of wood-decaying fungi from the 'Antrodia clade' (Polyporales, Agaricomycetes) on three different wood substrates (pine, spruce, and aspen) in submerged cultures. We identified dozens to hundreds of substrate-biased genes (i.e., genes that are significantly upregulated in one substrate relative to the other two substrates) in each species, and these biased genes are correlated with their host ranges. Evolution of substrate-biased genes is associated with gene family expansion, gain and loss of genes, and variation in cis- and trans- regulatory elements, rather than changes in protein coding sequences. We also demonstrated widespread RNA editing events in the Antrodia clade, which differ from those observed in the Ascomycota in their distribution, substitution types, and the genomic environment. Moreover, we found that substrates could affect editing positions and frequency, including editing events occurring in mRNA transcribed from wood-decay-related genes. This work shows the extent to which gene expression and RNA editing differ among species and substrates, and provides clues into mechanisms by which wood-decaying fungi may adapt to different hosts.

Comparative transcriptomic analysis of Cerrena unicolor revealed differential expression of genes engaged in degradation of various kinds of wood

To explore the number of enzymes engaged by Cerrena unicolor FCL139 for wood degradation, the transcriptomes of the fungus growing on birch, ash, maple sawdust and the control liquid medium were analyzed. Among 12,966 gene models predicted for the C. unicolor genome, 10,396 all-unigenes were detected, of which 9567 were found to be expressed in each of the tested growth media. The highest number (107) of unique transcripts was detected during fungus growth in the control liquid medium, while the lowest number (11) - in the fungal culture comprising maple saw dust. Analysis of C. unicolor transcriptomes identified numerous genes whose expression differed substantially between the mycelia growing in control medium and each of the sawdust media used, with the highest number (828) of upregulated transcripts observed during the fungus growth on the ash medium. Among the 294 genes that were potentially engaged in wood degradation, the expression of 59 was significantly (p < .01) changed in the tested conditions. The transcripts of 37 of those genes were at least four times more abundant in the cells grown in all sawdust media when compared to the control medium. Upregulated genes coding for cellulases and, to a lower extent, hemicellulases predominated during fungus growth on sawdust. Transcripts encoding cellulolytic enzymes were the most abundant in mycelia grown on birch and maple while lower number of such transcripts was detected in fungus growing on ash. The expression pattern of lignolytic activities-coding genes was strongly dependent on the type of sawdust applied for fungus growth medium.