Cloning of a novel type III polyketide synthase encoded by a three-intron gene from Polygonum cuspidatum

By using the TAIL-PCR and over-hang extension PCR methods, we successfully isolated a three-intron type III PKS gene and cDNA clone from the Polygonum cuspidatum Sieb. et Zucc, and named it PcPKS4. The phylogenetic analysis showed that PcPKS4 is located in a cluster containing all functionally divergent CHS-like enzymes from angiosperms. Interestingly, the CHS “gatekeeper” phenylalanine, Phe265 is uniquely replaced by Leu in PcPKS4. Different from our previously results, RNA gel–blot analysis revealed that the PcPKS4 transcripts were present at a low level in roots.