Cuphea wrightii thioesterases have unexpected broad specificities on saturated fatty acids

Area of Science:

• Plant biochemistry
• Seed lipid metabolism
• Fatty acid biosynthesis

Background:

• Cuphea wrightii seeds accumulate high levels of caprate (10:0) and laurate (12:0).
• Acyl-acyl carrier protein (ACP) thioesterases (TEs) are key enzymes in regulating fatty acid chain length during seed oil synthesis.

Purpose of the Study:

• To investigate the role of two specific TEs, Cw FatB1 and Cw FatB2, in determining acyl chain length in Cuphea wrightii seed lipids.
• To understand if these TEs are solely responsible for the unique fatty acid profile of C. wrightii.

Main Methods:

• Isolation and characterization of Cw FatB1 and Cw FatB2 cDNAs from C. wrightii embryos.
• Expression analysis of Cw FatB1 and Cw FatB2 in different tissues.
• Functional analysis of Cw FatB1 and Cw FatB2 in transgenic Arabidopsis to determine their substrate specificity and product profiles.
• Analysis of gene dosage effects on fatty acid production in C. wrightii progeny.

Main Results:

• Cw FatB1 and Cw FatB2 were detected in developing embryos and mature seeds, indicating their role in seed oil synthesis.
• Transgenic Arabidopsis expressing Cw FatB1 and Cw FatB2 produced a range of fatty acids (12:0, 14:0, 16:0), with a preference for 14:0, and Cw FatB2 also produced some 10:0.
• Increased expression levels of these TEs in vivo had a minimal impact on diverting fatty acid production towards shorter chains.

Conclusions:

• Cw FatB1 and Cw FatB2 are likely involved in the unique fatty acid composition of Cuphea wrightii seeds.
• These TEs are necessary but not sufficient to fully explain the specific accumulation of caprate and laurate in C. wrightii lipids.
• Other regulatory factors likely contribute to the precise control of fatty acid chain length in this species.