Identification of novel acyl-ACP thioesterase gene ClFATB1 from Cinnamomum longepaniculatum.
A putative fatty acyl-acyl carrier protein (acyl-ACP) thioesterase (thioesterase) full-length cDNA sequence named as ClFATB1 was obtained from the seed cDNA library of Cinnamomum longepaniculatum by the SMART-RACE method. The novel gene encodes a protein of 382 amino acid residues with close homology to fatty acid thioesterase type B (FATB) enzymes of other plants, with two essential residues (His285 and Cys320) for thioesterase catalytic activity. The gene was transcribed in all tissues of C. longepaniculatum, the highest being in seeds. Recombinant ClFATB1 in Escherichia coli had higher specific activities against saturated 16:0- and 18:0-ACPs than on unsaturated 18:1-ACP. Overexpression of ClFATB1 in transgenic tobaccos upregulated thioesterase activities of crude proteins against 16:0-ACP and 18:0-ACP by 20.3 and 5.7%, respectively, and resulted in an increase in the contents of palmitic and stearic acids by 15.4 and 10.5%, respectively. However, ectopic expression of this gene decreased the substrate specificities of crude proteins to unsaturated 18:1-ACP by 12.7% in transgenic tobacco and lowered the contents of oleic, linoleic, and linolenic acids in transgenic leaves. So ClFATB1 would potentially upregulate the synthesis of saturated fatty acids and downregulate unsaturated ones in the fatty acid synthesis pathway of plants.
Key Laboratory of Bio-resources and Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, P. R. China. wangshenghua24@163.com.
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D000213:Acyl Carrier Protein / Q000378:metabolism; D000595:Amino Acid Sequence; D027424:Cinnamomum / Q000145:classification / Q000235:genetics*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D005227:Fatty Acids / Q000032:analysis / Q000378:metabolism; D015723:Gene Library; D008969:Molecular Sequence Data; D010802:Phylogeny; D018515:Plant Leaves / Q000201:enzymology / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013869:Thiolester Hydrolases / Q000235:genetics* / Q000378:metabolism; D014026:Nicotiana / Q000378:metabolism
D000213:Acyl Carrier Protein; D018076:DNA, Complementary; D005227:Fatty Acids; D010940:Plant Proteins; D013869:Thiolester Hydrolases