[Isolation and charcterizaiton of a polyketide synthase gene cluster from Usnea longissima].

OBJECTIVE

To isolate polyketide synthase (PKS) gene from medicinal Usnea longissima lichen forming fungi, and identify the function of obtained PKS.

METHODS

We used Usnea. longissima lichen forming fungi to isolate PKS gene by nested PCR using degenerate primers and screening a Fosimid genomic library. MEGA 4.0.2 program was used for phylogenetic analysis and RT-PCR was used to detect gene expression.

RESULTS

We obtained a gene cluster including non-reducing PKS (UlPKS5), putative beta-lactamase and putative dehydratase from Usnea longissima lichen forming fungi. UlPKS5 contained ketosynthase (KS), acyl transferase (AT), product template (PT) and acyl carrier protein (ACP) domain. Phylogenetic analysis shows that UlPKS5 belonged to non-reducing PKS group V, which involved anthraquinone biosynthesis. RT-PCR analyses reveal that the expression of UlPKS5 was up-regulated by sucrose (2% and 10%) and sorbitol (10%).

CONCLUSIONS

PKS(UlPKS5), putative beta-lactamase and putative dehydratase were related with anthraquinone biosynthesis in U. longissima.