Abstract:
While microbial colonization of wood is presumed to be characterized by a
myriad of interactions between numerous organisms, studying these processes is
often difficult owing to the opaque nature of the wood and the inability to readily
distinguish among the many species colonizing the material. One method for
enhancing the ability to distinguish organisms is to induce specific proteins in one
or more organisms that can be detected using fluorescence or other light
microscopic techniques. The insertion of genes for the production of green
fluorescent proteins produced by the jellyfish, Aequora victoria, has been widely
used to visualize a variety of organisms. In this study, an important wood sapstain
fungus, Ophiostoma piceae, and its biocontrol agent, Trichoderma harzianum
were transformed using a green fluorescent protein (SGFP) gene under the control
of the ToxA promoter of Pyrenophora tritici-repentis. Spore germination and
growth developments of these fungi on freshly sawn Douglas-fir sapwood were
examined using fluorescence microscopy. The expression of gfp was particularly
useful for studying the spatial distribution of young hyphae in wood.
The gfp transformants were used to study interactions between T
harzianum and 0. piceae in freshly sawn Douglas-fir sapwood. 0. piceae growth
decreased with increasing spore ratios of T harzianum to 0. piceae. Prior
establishment of T. harzianum was effective against 0. piceae growth on Douglas-fir
sapwood, but killing established T. harzianum by [gamma] irradiation eliminated this
effect. Killing T harzianum by autoclaving after prior establishment afforded
partial protection against 0. piceae growth. The results illustrate the potential role
of active growth in biocontrol against stain fungi.
