Abstract
Fatty acyl-acyl thioesterases (FATs), which hydrolyze the thioester bond linking acyl chains to an acyl carrier protein, thereby terminating their elongation, contribute significantly to the fatty acid (FA) content and composition of seed storage lipids. The peanut (Arachis hypogaea L.) genome was found to harbor 21 FAT (AhFAT) genes, distributed over 12 of the 20 chromosomes. The length of their predicted translation products varied from 74 to 415 residues, and all but one included the 1–2 Acyl-ACP_TE conserved domains. All of the coding sequences were interrupted by at least one intron, with the exon number ranging from two to 12, and five of the genes were liable to alternative splicing. When the RNA-Seq platform was used to assess the transcriptional behavior of the 21 AhFAT genes, transcription of only 13 was detectable in samples of root, leaves, and developing seed; among these, six were transcribed throughout the plant, three were root-specific and one was leaf-specific. A detailed analysis of a pair of homologous AhFATs showed that the coding region of each was split into six exons and that both were transcribed in all of the plant organs surveyed (although the intensity of their transcription was not the same in immature seed). The product of both genes was deposited in the chloroplast outer membrane. The constitutive expression of these genes in either yeast or Arabidopsis thaliana increased the FA content, especially that of saturated FAs. In peanut genome, 21 AhFAT genes were found and two of them were transformed into yeast and Arabidopsis for function identification. Results showed that overexpression of these two genes could increase the FA content, especially the saturated FAs content.
Highlights
C18:0 Stearic acid C18:1 Oleic acid C18:2 Linoleic acid C18:3 Linolenic acid C20:0 Arachidic acid C20:1 Eicosenoic acid C20:2 Eicosadienoic acid C22:1 Erucic acid fatty acid (FA) Fatty acid Fatty acyl-acyl carrier protein thioesterases (FATs) Fatty acyl-acyl thioesterase RT-PCR Real-time quantitative polymerase chain reaction Taqman-PCR Taqman-polymerase chain reaction
The genetic manipulation of various plant FAT genes has been shown to influence FA composition: for example, the overexpression of the Arabidopsis thaliana gene AtFATB1 results in the accumulation of 1 Palmitoleic acid (C16):0 (Dörmann et al 2000)
21 potential AhFATs were uncovered from A. hypogaea genome (Supplemental Table S3); four loci mapped to each of chromosomes Arahy.12 and Arahy.13, three to Arahy.01, two to Arahy.02, and the other eight each
Summary
C18:0 Stearic acid C18:1 Oleic acid C18:2 Linoleic acid C18:3 Linolenic acid C20:0 Arachidic acid C20:1 Eicosenoic acid C20:2 Eicosadienoic acid C22:1 Erucic acid FA Fatty acid FAT Fatty acyl-acyl thioesterase RT-PCR Real-time quantitative polymerase chain reaction Taqman-PCR Taqman-polymerase chain reaction. Introduction algal species has been shown to be effective in both altering the FA profile and increasing the content of a number of FAs (Chen et al 2017). When a FATB gene isolated from the cigar plant Cuphea lanceolata was expressed in C. reinhardtii, the production of C14:0 (Myristic acid)-containing triacylglycerols increased by up to 1.6-fold (Inaba et al 2017). The heterologous expression of a Brassica napus FATB gene in yeast raised the content of the saturated C16:0 and C18:0 (stearic acid) by, respectively, 46% and 22%, at the same time reducing that of both the unsaturated C16:1 (palmitoleic acid) and C18:1 (oleic acid) by, respectively, 15% and 31% (Tan et al 2015). Several genes influencing its seed oil content have been identified, among which are a number of FATs. The expression of an AhFATAin both Escherichia coli and certain
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