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| Usnea longissima has a long history of use as a traditional
medicine. Several bioactive compounds, primarily belonging to the
polyketide family, have been isolated from U. longissima.
However, the genes for the biosynthesis of these compounds are yet to be
identified. In the present study, three different types of non-reducing
polyketide synthases (UlPKS2, UlPKS4, and UlPKS6) were identified from a
cultured lichen-forming fungus of U. longissima. Phylogenetic
analysis of product template domains showed that UlPKS2 and UlPKS4
belong to group IV, which includes the non-reducing polyketide synthases
with an methyltransferase (MeT) domain that are involved in
methylorcinol-based compound synthesis; UlPKS6 was found to belong to
group I, which includes the non-reducing polyketide synthases that
synthesize single aromatic ring polyketides, such as orsellinic acid.
Reverse transcriptase-PCR analysis demonstrated that UlPKS2 and UlPKS4
were upregulated by sucrose; UlPKS6 was downregulated by asparagine,
glycine, and alanine. |
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