Comparative analysis of basidiomycetous laccase genes in forest soils reveals differences at the cDNA and DNA levels.

Aims: This study was undertaken to investigate laccase-containing basidiomycete communities at the cDNA and DNA levels and to assess the influences of vegetation and soil types on the basidiomycete communities in forest soils. Materials and methods: Soil samples were collected from the upper soil layers of two typical subtropical forests (a broad-leaved forest developed in Karst limestone soil and an artificial coniferous forest with Pinus massoniana in red soil) in China. The basidiomycete communities were characterized by cloning and sequencing of the laccase genes at both the cDNA and DNA levels. Compositions of lignin monomers were determined by gas chromatography-mass spectrometry. Results: Most of the laccase genes obtained in this study were new, highlighting the research gap of this functional group. The trends of the basidiomycetous laccase gene diversity among the upper soil layers of the two forests were consistent between the cDNA and DNA levels. The Agaricales had high activity because they dominated all the tested soils. However, the total basidiomycete communities reflected at the cDNA and DNA levels were significantly different due to the presence of some quiescent basidiomycetous groups. Almost all of the lignin components were decomposed from the O to the A layers in the two forests, and laccases produced by Agaricales were likely responsible for the decomposition of guaiacyl monomers. Both vegetation and soil types had great influences on the active laccase-containing basidiomycete communities, primarily via the pH, C/N, and the contents of lignin monomers. Conclusions: The cDNA- and DNA-level approaches presented good consistency of diversities but different compositions of laccase-containing basidiomycete communities, thus emphasizing the importance of focusing on laccase genes at the cDNA level in future studies. It is the quality but not the quantity of SOM to determine the diversity and composition of the active laccase-containing basidiomycete communities. [ABSTRACT FROM AUTHOR]