PNNL

Abstract

Wood-degrading fungi use a sequence of oxidative and hydrolytic mechanisms to loosen lignocellulose and then release and metabolize embedded sugars. These temporal sequences have recently been mapped at high resolution using directional growth on wood wafers, revealing previously obscured dynamics as fungi progressively colonize wood. Here, we applied secretomics in the same wafer design to track temporal trends on aspen decayed by fungi with distinct nutritional modes: two brown rot-type (BR) fungi (Postia placenta, Gloeophyllum trabeum) and two white rot (WR) (Stereum hirsutum, Trametes versicolor). We matched secretomic data from three zones of decay (early, middle, late) with enzyme activities in these zones, and we included measures of total protein and ergosterol as benchmarks. In line with previous transcriptomics data, all of fungi tested showed an initial investment in pectinases and a delayed investment in other glycoside hydrolases (GHs). Brown rot fungi also staggered abundance of some oxidoreductases ahead of GHs to produce a familiar two-step mechanism. White rot fungi, however, showed late-stage investment in pectinases as well, unlike brown rot fungi. Lignolytic enzyme activities and abundances were also different between the two white rot fungi. Specifically, S. hirsutum lignolytic activity was delayed, explained almost entirely by the activity and abundance of five ‘atypical’ type manganese peroxidases, unlike more varied peroxidases and laccases in T. versicolor. These secretomic analyses support brown rot patterns generated via transcriptomics, they reveal distinct patterns among and within rot types, and they link spectral counts with activities to help functionalize these multi-strain secretomic data.