Screening of basidiomycetes and gene expression of selected lignin modifying enzymes of Phlebia radiata during biodeterioration of three wood types

Abstract

Gene expression studies were conducted on selected decay enzymes during the decay of pine, cedar, and alkaline copper quaternary (ACQ)-treated pine over 18 months. Measurements of modulus of elasticity (MOE), decay rating, and moisture content were also monitored. After 4 months in a soil bed decay test, identification of decay fungi was made to determine gene expression levels. The white rot fungus, Phlebia radiata was identified on all wood stakes. Therefore, P. radiata species specific primers were designed to track the expression of three decay enzyme genes: lignin peroxidase (Lip), manganese peroxidase (Mnp), and laccase (Lcc) on wood samples. The gene expression of Lip and Mnp was similar on pine and on ACQ-treated pine but no Lip or Mnp was expressed on cedar throughout the study. There was significantly more Lcc produced on ACQ-treated pine stakes at 6, 8, 16, and 18 months than pine stakes while no Lcc was expressed on cedar. Basidiomycete decay genes were present on ACQ-treated pine and decay fungi colonized ACQ-treated pine but caused little if any wood decay. Thus, it appears ACQ-treated wood does not stop the expression of the decay genes but does inhibit the effectiveness of the enzymes. No basidiomycete genes were expressed and few basidiomycetes colonized cedar and little or no decay was observed on cedar. The results show that the naturally durable cedar reduced the wood decay community and gene expression in comparison to untreated pine and ACQ-treated pine. To our knowledge, this is the first report that describes decay enzyme gene expressions on chemically and naturally durable woods in forest soils.