Temporal changes in diversity and expression patterns of fungal laccase genes within the organic horizon of a brown forest soil

Temporal fluctuations of present and expressed fungal genes encoding the ligninolytic enzyme laccase were examined bimonthly between March 2004 and April 2005 in the organic horizon of a beech forest Cambisol. Using two sets of degenerate primer pairs, we detected 73 different basidiomycete laccase genes from soil DNA extracts and 42 different transcripts of asco- and basidiomycetes from soil RNA extracts (cDNA). Phylogenetic analysis related the sequences to fungal taxa. The highest fungal laccase gene richness in soil DNA and RNA samples were found in August, October and January, and followed the input of fresh litter into soil. The highest change of the fungal laccase gene population was observed from October to January, but no distinct temporal change in the total soil laccase activity was measured. Present and expressed laccase gene populations were highly different, implying different subsets amplified with our primer sets and likely impacting future research strategies. Despite considerable variations in gene presence and expression, we found a steady expression and high soil enzyme activity of fungal laccases at each sampling date, thus presumably laccases have major impacts to soil organic matter turnover and stabilization processes.