Abstract
BackgroundPlant seed oil is an important bioresource for human food and animal feed, as well as industrial bioproducts. Therefore, increasing oil content in seeds has been one of the primary targets in the breeding programs of oilseed crops. Thraustochytrium is a marine protist that can produce a high level of very long-chain polyunsaturated fatty acids (VLCPUFAs) using a PUFA synthase, a polyketide synthase-like fatty acid synthase with multiple catalytic domains. Our previous study showed that a KS domain from the synthase could complement an Escherichia coli mutant defective in β-ketoacyl-ACP synthase I (FabB) and increase the total fatty acid production. In this study, this KS domain from the PUFA synthase was further functionally analyzed in Arabidopsis thaliana for the capacity of oil production.ResultsThe plastidial expression of the KS domain could complement the defective phenotypes of a KASI knockout mutant generated by CRISPR/Cas9. Seed-specific expression of the domain in wild-type Arabidopsis significantly increased seed weight and seed oil, and altered the unsaturation level of fatty acids in seeds, as well as promoted seed germination and early seedling growth.ConclusionsThe condensation process of fatty acid biosynthesis in plants is a limiting step, and overexpression of the KS domain from a PUFA synthase of microbial origin offers a new strategy to increase oil production in oilseed plants.
Highlights
Plant seed oil is an important bioresource for human food and animal feed, as well as industrial bioproducts
Fatty acid biosynthesis occurs in plastids where acetyl-CoA carboxylase (ACCase) catalyzes the formation of malonyl-CoA from acetyl-CoA initially, and a type II fatty acid synthase (FAS) complex uses malonyl thioester as an extender for the synthesis of long-chain saturated fatty acids such as 16:0 and 18:0 through a repetitive cycle of four catalytic reactions: condensation, keto-reduction, dehydration and enoyl-reduction [10]
The results showed that the ketoacyl-ACP synthase (KS) domain was functional in the plant and able to complement the defective phenotype of an Arabidopsis ketoacyl-ACP synthase I (KASI) knockout mutant generated by clustered regularly interspaced short palindromic repeats/ CRISPR-associated protein-9 nuclease (CRISPR/Cas9), and the seed-specific expression of this domain in wildtype Arabidopsis significantly enhanced seed weight and seed oil and promoted seed germination and seedling growth
Summary
Plant seed oil is an important bioresource for human food and animal feed, as well as industrial bioproducts. Fatty acid biosynthesis occurs in plastids where acetyl-CoA carboxylase (ACCase) catalyzes the formation of malonyl-CoA from acetyl-CoA initially, and a type II fatty acid synthase (FAS) complex uses malonyl thioester as an extender for the synthesis of long-chain saturated fatty acids such as 16:0 and 18:0 through a repetitive cycle of four catalytic reactions: condensation, keto-reduction, dehydration and enoyl-reduction [10]. After synthesis, these two long-chain fatty acids are often desaturated by a soluble acyl-ACP Δ9-desaturase in the stroma of plastids giving 16:1–9 and 18:1–9. With few exceptions [11], higher plants do not possess capacity to synthesize very long-chain polyunsaturated fatty acids (VLCPUFAs) with the chain length of 20C or more and the double bonds of two or more
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