Structural and functional variation in soil fungal communities associated with litter bags containing maize leaf.

Soil fungi are key players in the degradation of recalcitrant organic matter in terrestrial ecosystems. To examine the organisms and genes responsible for complex organic matter degradation in soil, we tracked changes in fungal community composition and expressed genes in soil adjacent to mesh bags containing maize leaves undergoing decomposition. Using high-throughput sequencing approaches, changes in fungal community composition were determined by targeting 18S rRNA gene sequences, whereas community gene expression was examined via a metatranscriptomic approach. The majority of the 93 000 partial 18S rRNA gene sequences generated, were affiliated with the Ascomycota and Basidiomycota. Fungal diversity was at least 224 operational taxonomic units at the 97% similarity cutoff level. During litter degradation, the relative proportion of Basidiomycota increased, with a decrease in Ascomycota : Basidiomycota ratios over time. The most commonly detected decomposition-associated fungi included Agaricomycetes and Tremellales as well as unclassified Mucoromycotina. The majority of protein families found in the metatranscriptomic data were affiliated to fungal groups described to degrade plant-derived cellulose, such as Mucoraceae, Chaetomiaceae, Sordariaceae, Sebacinaceae, Tremellaceae, Psathyrellaceae and Schizophyllaceae. The combination of high-throughput rRNA gene-based and metatranscriptomic approaches provided perspectives into the organisms and genes involved in complex organic matter in soil.