Pestalotiopsis micmspora was isolated from the inner bark of a small limb of Himalayan yew, Taxus wallachiana, and was shown to produce taxol in mycelial culture. Taxol was identified by spectroscopic and chromatographic comparisons with authentic taxol. Optimal taxol production occurred after 2-3 weeks in still culture at 23 O C .[I4C]Acetate and [14C]phenylalanine served as precursors for fungal [14C]taxol. These observations on P. micmspora are discussed in relation to the biological importance of taxol production by fungi in general.
Pestalotiopsis microspora occurs as a range of strains in bald cypress, Taxodium distichurn. The organisms live as endophytes in the bark, phloem and xylem, and isolates show differences in cultural and microscopic characteristics on common laboratory media. Many of these fungi make taxol as determined by the reactivity of partially purified culture extracts with specific monoclonal antibodies against taxol. In the case of one strain of P. microspora (CP-4), taxol was isolated from culture medium and was shown to be identical to authentic taxol by chromatographic and spectroscopic means.
Wollemia nobilis (Wollemi pine), an araucariaceous
plant, whose closest known relatives are from the Jurassic period, occurs in
the Wollemi National Park near Sydney, Australia. This tree is host to many
endophytic fungi, including Pestalotiopsis guepinii
which produces taxol, an important anticancer drug. It was shown by
immunological, spectroscopic and chromatographic means to be identical with
authentic taxol obtained from Taxus brevifolia (Pacific
yew). Since the Wollemi pine does not produce taxol, how might a
taxol-producing fungus be present in this unusual tree? Spores of
P. guepinii possess several appendages which strongly
interact with hydrophobic surfaces including plastics and the pinnae of
birds’ feathers. Scanning electron microscopy of the conidia of
P. guepinii clearly shows the spores on the feathers of
a green-checked conure and a cockatiel. Conceivably, the fungus may have
acquired the ability to produce taxol from a foreign or local yew and then is
carried to the Wollemi pine site by native birds.
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