Planta

, 229:457

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

  • Lan-Qing Ma
  • Xiao-Bin Pang
  • Hai-Yan Shen
  • Gao-Bin Pu
  • Hua-Hong Wang
  • Cai-Yan Lei
  • Hong Wang
  • Guo-Feng Li
  • Ben-Ye Liu
  • He-Chun Ye
Original Article

DOI: 10.1007/s00425-008-0845-7

Cite this article as:
Ma, L., Pang, X., Shen, H. et al. Planta (2009) 229: 457. doi:10.1007/s00425-008-0845-7

Abstract

A type III polyketide synthase cDNA and the corresponding gene (PcPKS2) were cloned from Polygonum cuspidatum Sieb. et Zucc. Sequencing results showed that the ORF of PcPKS2 was interrupted by three introns, which was an unexpected finding because all type III PKS genes studied so far contained only one intron at a conserved site in flowering plants, except for an Antirrhinum majus chalcone synthase gene. Besides the unusual gene structure, PcPKS2 showed some interesting characteristics: (1) the CHS “gatekeepers” Phe215 and Phe265 are uniquely replaced by Leu and Cys, respectively; (2) recombinant PcPKS2 overexpressed in Escherichia coli efficiently afforded 4-coumaroyltriacetic acid lactone (CTAL) as a major product along with bis-noryangonin (BNY) and p-hydroxybenzalacetone at low pH; however, it effectively yielded p-hydroxybenzalacetone as a dominant product along with CTAL and BNY at high pH. Beside p-hydroxybenzalacetone, CTAL and BNY, a trace amount of naringenin chalcone could be detected in assays at different pH. Furthermore, 4-coumaroyl-CoA and feruloyl-CoA were the only cinnamoyl-CoA derivatives accepted as starter substrates. PcPKS2 did not accept isobutyryl-CoA, isovaleryl-CoA or acetyl-CoA as substrate. DNA gel blot analysis indicated that there are two to four PcPKS2 copies in the P. cuspidatum genome. RNA gel blot analysis revealed that PcPKS2 is highly expressed in the rhizomes and in young leaves, but not in the roots of the plant. PcPKS2 transcripts in leaves were induced by pathogen infection, but not by wounding.

Keywords

Benzalacetone synthasep-Coumaroyl triacetic acid synthaseIntronPolygonumPolyketide synthase

Abbreviations

ALS

Aloesone synthase

BAS

Benzalacetone synthase

CHS

Chalcone synthase

CoA

Coenzyme A

CTAS

p-Coumaroyl triacetic acid synthase

LC-ESIMS

Liquid chromatography electron spray ionization mass spectrometry

OKS

Octaketide synthase

PKS

Polyketide synthase

STS

Stilbene synthase

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • Lan-Qing Ma
    • 1
    • 2
  • Xiao-Bin Pang
    • 2
  • Hai-Yan Shen
    • 1
  • Gao-Bin Pu
    • 1
  • Hua-Hong Wang
    • 1
  • Cai-Yan Lei
    • 1
  • Hong Wang
    • 1
  • Guo-Feng Li
    • 1
  • Ben-Ye Liu
    • 1
  • He-Chun Ye
    • 1
  1. 1.Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of BotanyThe Chinese Academy of SciencesBeijingPeople’s Republic of China
  2. 2.College of Plant ScienceJilin UniversityChangchunPeople’s Republic of China