A novel type III polyketide synthase encoded by a three-intron gene from Polygonum cuspidatum.
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.
Ma
Lan-Qing
LQ
The Chinese Academy of Sciences, Xiangshan, Haidian District, 100093, Beijing, People's Republic of China.
Pang
Xiao-Bin
XB
Shen
Hai-Yan
HY
Pu
Gao-Bin
GB
Wang
Hua-Hong
HH
Lei
Cai-Yan
CY
Wang
Hong
H
Li
Guo-Feng
GF
Liu
Ben-Ye
BY
Ye
He-Chun
HC
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary; D045468:Fallopia japonica / Q000201:enzymology* / Q000235:genetics; D015870:Gene Expression; D017343:Genes, Plant; D007438:Introns; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D048630:Polyketide Synthases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein
D018076:DNA, Complementary; D010940:Plant Proteins; D048630:Polyketide Synthases