Genomic and Experimental Investigations of Auriscalpium and Strobilurus
Fungi Reveal New Insights into Pinecone Decomposition
Abstract
Saprophytic fungi play vital roles in nutrient cycling and ecosystem
dynamics. However, our understanding of how saprophytic fungi interact
with each other to decompose organic matter is very limited. Here, we
conducted field surveys of pinecone-colonizing/decomposing mushrooms,
investigated the chemical compositions of decomposing pinecones, and
analyzed seven new genomes of three pairs of mushrooms in the genera
Auriscalpium and Strobilurus with substrate specificities. Each pair of
mushrooms successively colonizes the pinecones of a different pine
species: A. orientale-S. luchuensis on Pinus yunnanensis, A. vulgare-S.
stephanocystis on Pinus sylvestris, and A. microsporum-S.
pachcystidiatus/S. orientalis on Pinus armandii. Our analyses revealed
evidence for both competition and cooperation between Auriscalpium and
Strobilurus fungi during pinecone decomposition. Their successive
colonization of the two fungi groups with complementary profiles of
carbohydrate-active enzymes enabled efficient decomposition and
utilization of pinecones. The Auriscalpium fungi are highly effective at
utilizing the recalcitrant primary organic carbons such as lignin and
hemicellulose in freshly fallen pinecones. The decomposition by
Auriscalpium fungi enabled the successive colonization by Strobilurus
fungi which can produce an arsenal of secondary metabolites such as
strobilurins to inhibit other fungi and have abundant
carbohydrate-active enzymes for effective utilization of the remaining
organic compounds in pinecones.