Tri-Hydroxy-Triacylglycerol Is Efficiently Produced by Position-Specific Castor Acyltransferases

Area of Science:

• Plant biochemistry
• Metabolic engineering
• Seed oil modification

Background:

• Understanding triacylglycerol (TAG) assembly is key for tailoring seed oils.
• Hydroxy-fatty acids (HFAs) are valuable modified fatty acids.
• Transgenic expression of castor hydroxylase in Arabidopsis yields low HFA-TAG and poor seedling establishment due to inefficient metabolic networks.

Purpose of the Study:

• To enhance the biosynthesis and catabolism of hydroxy-containing TAGs in Arabidopsis.
• To improve the production of high-value modified seed oils.

Main Methods:

• Transgenic expression of three castor acyltransferase enzymes in Arabidopsis seeds.
• Incorporation of HFA at each stereochemical position during TAG synthesis.
• Analysis of TAG composition, HFA content, seed oil content, and seedling establishment.

Main Results:

• Abundant tri-HFA TAG production, with 44% of seed HFA concentrated in this species.
• Ricinoleic acid became the most abundant fatty acid, yielding 3-fold more HFA by weight than previous methods.
• Efficient HFA utilization doubled TAG synthesis rate, resolving the low-oil phenotype.
• Increased storage lipid availability led to a 1.9-fold improvement in seedling establishment.

Conclusions:

• Expression of a complete acyltransferase pathway efficiently processes HFA for TAG synthesis.
• This metabolic engineering approach establishes a benchmark for producing modified seed oils in plants.
• Successfully improved seed oil quality and plant viability by enhancing lipid metabolism.