Cell wall alterations in loblolly pine wood decayed by the white-rot fungus, Ceriporiopsis subvermispora

Abstract

Ultrastructural, immunocytochemical and UV absorption spectroscopy techniques were used to elucidate the progressive changes that occur within woody cell walls during decay by Ceriporiopsis subvermispora. After only 2 weeks of incubation, uranyl acetate staining revealed a diffuse electron dense zone in the secondary wall near hyphae and around the outer circumference of the wall. The extent of cell wall staining increased with longer fungal incubation. No staining occurred in sound unaltered cell walls. Proteins of varying molecular weights (insulin, 5730 Da; myoglobin, 17 600 Da; ovalbumin, 44 287 Da) were infiltrated into sound and decayed wood followed by immunogold labelling and transmission electron microscopy. Insulin readily penetrated into the outer most regions of secondary walls of wood cells after 2 weeks of decay. Myoglobin was first observed to penetrate cell walls at 4 weeks of degradation and ovalbumin was found after 8 weeks in wood with advanced stages of decay where extensive cell wall disruption was evident. None of the proteins used were localized within cell walls of untreated, control wood samples. UV microspectrophotometry demonstrated a progressive loss of absorbance at 240 and 280 nm within the secondary walls and middle lamellae at various sampling times throughout the duration of the decay study.