Identification and characterization of type III polyketide synthase genes from culturable endophytes of ethnomedicinal plants

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>Endophytic fungi provide benefits to host plants by producing a diverse class of secondary metabolites (natural products). Arrays of polyketide natural products are synthesized by specific classes of polyketide synthases (PKS I, II and III) in host organisms. In the present study, we attempt to screen and identify type III PKSs in culturable fungal endophytes isolated from the ethno medicinal plants including <I>Arbus precatorius</I>, <I>Bacopa monnieri,Citrus aurantifolia</I> and <I>Datura metel</I> to detect the genetic potential of endophytic fungi in producing bioactive compounds. A total of seventeen endophytic fungal strains belonging to eight genera were identified using fungal morphology and rDNA-ITS phylogenetic analyses. A CODEHOP-PCR based strategy was followed to design degenerate primers for the screening of type III PKS genes from fungal endophytes. We had successfully amplified partial PKS genes from eight endophytes. The amplified PKS sequences showed 60–99% identity to already characterized/putative PKS genes. From the partial sequence of FiPKS from <I>Fusarium incarnatum</I> BMER1, a full-length gene was amplified, cloned and characterized. FiPKScDNA was cloned and expressed in <I>E. coli</I> Lemo21 (DE3) and the purified protein was shown to produce pyrones and resorcinols using acyl-CoA thioesters as substrates. FiPKS showed the highest catalytic efficiency of 7.6 × 10<SUP>4</SUP> s<SUP>−1</SUP> M<SUP>-1</SUP> with stearoyl CoA as a starter unit. This study reports the identification and characterization of type III PKS from endophytes of medicinal plants by CODEHOP PCR.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A CODEHOP PCR based screening method was employed for type III polyketide synthase gene identification in fungal endophytes. </LI> <LI> By this approach, partial type III PKS genes from eight fungal endophytes were amplified and sequenced. </LI> <LI> FiPKS gene from Fusarium incarnatum BMER1, an endophyte of Bacopa monnieri was cloned and functionally characterized. </LI> <LI> FiPKS produced pyrones and resorcinols with the highest catalytic efficiency of 7.6 x 104 s-1 M-1towards stearoyl CoA. </LI> </UL> </P>