Use of immunogold cytochemistry to detect Mn(II)-dependent and lignin peroxidases in wood degraded by the white rot fungi Phanerochaete chrysosporium and Lentinula edodes

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Abstract
Using antibodies raised against Mn(II)-dependent peroxidase and transmission electron microscopy immunogold cytochemistry, the spatial distribution of Mn(II)-dependent peroxidase during degradation of wood and wood fragments by Phanerochaete chrysosporium and Lentinula edodes was studied. In P. chrysosporium, the enzyme was localized in peripheral regions of the fungal hyphae on the cell membrane, on membranes of vesicule-like structures, and on the cell wall. The cytoplasmic distribution of Mn(II)-dependent peroxidase appeared similar to that of lignin peroxidase, as determined by double immunogold labeling procedures and antibodies raised against lignin peroxidase. In wood blocks of Betula verrucosa degraded by P. chrysosporium and L. edodes, Mn(II)-dependent peroxidase was detected on all wood cell wall layers showing signs of decay, whether at early or advanced stages of attack. In particular, the enzyme was localized in zones of degradation produced within the S2 wood cell walls. These regions displayed a looser, more open fibrillar structure than unattacked wood cell walls and were readily penetrated by purified preparations of Mn(II)-dependent and lignin peroxidases. With L. edodes, Mn(II)-dependent peroxidase was found to accumulate in middle lamellar regions selectively degraded by the fungus. Mn(II)-dependent peroxidase diffusion into undecayed wood cell walls was not observed. Key words: Mn(II)-dependent peroxidase, Phanerochaete chrysosporium, Lentinula edodes, immunogold cytochemistry, white rot decay, transmission electron microscopy.