Functional characterization of a plastidal cation-dependent O-methyltransferase from the liverwort Plagiochasma appendiculatum.
Caffeoyl CoA O-methyltransferases (CCoAOMTs), known to be involved in phenylpropanoid metabolism and lignin synthesis, have been characterized from several higher plant species, which also harbor CCoAOMT-like enzymes responsible for methylation of a variety of flavonoids, anthocyanins, coumarins and phenylpropanoids. Here, a gene encoding a CCoAOMT (PaOMT1) was isolated from a sequenced cDNA library of the liverwort species Plagiochasma appendiculatum, a species belonging to the Family Aytoniaceae. The full-length cDNA sequence of PaOMT1 contains 909 bp, and is predicted to encode a protein with 302 amino acids. The gene products were 40-50% identical to CCoAOMT sequences of other plants. Experiments based on recombinant PaOMT1 showed that the enzyme was able to methylate phenylpropanoids, flavonoids and coumarins, with a preference for the flavonoid quercetin (19). Although the substrate selectivity and biochemical feature of PaOMT1 is similar to CCoAOMT-like enzymes, the sequence alignment results indicated PaOMT1 is closer to true CCoAOMT enzymes. A phylogenetic analysis indicated that PaOMT1 is intermediate between true CCoAOMTs and CCoAOMT-like enzymes. The transient expression of a PaOMT1-GFP fusion in tobacco demonstrated that PaOMT1 is directed to the plastids. PaOMT1 may represent an ancestral form of higher plant true CCoAOMT and CCoAOMT-like enzymes. This is the first time an O-methyltransferase was characterized in liverworts.
Key Laboratory of Chemical Biology of Natural Products, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China.
Rui-Xue
RX
Xu
Key Laboratory of Chemical Biology of Natural Products, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China.
Yu
Y
Zhao
Key Laboratory of Chemical Biology of Natural Products, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China.
Shuai
S
Gao
Key Laboratory of Chemical Biology of Natural Products, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China.
Yu-Ying
YY
Zhang
Key Laboratory of Chemical Biology of Natural Products, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China.
Dan-Dan
DD
Li
Key Laboratory of Chemical Biology of Natural Products, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China.
Hong-Xiang
HX
Lou
Key Laboratory of Chemical Biology of Natural Products, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China. Electronic address: aixiacheng@sdu.edu.cn.
Ai-Xia
AX
Cheng
D000872:Anthocyanins / Q000737:chemistry; D002412:Cations; D003374:Coumarins / Q000737:chemistry; D018076:DNA, Complementary / Q000235:genetics; D005419:Flavonoids / Q000737:chemistry; D035926:Hepatophyta / Q000737:chemistry / Q000201:enzymology / Q000235:genetics; D008745:Methylation; D008780:Methyltransferases / Q000378:metabolism*; D010666:Phenylpropionates / Q000378:metabolism; D010802:Phylogeny
D000872:Anthocyanins; D002412:Cations; D003374:Coumarins; D018076:DNA, Complementary; D005419:Flavonoids; D010666:Phenylpropionates; D008780:Methyltransferases; C059825:caffeoyl-CoA O-methyltransferase
Aytoniaceae; Flavonoids; Liverworts; O-methyltransferase; Phenylpropanoids; Plagiochasma appendiculatum