Abstract
High amounts of polyunsaturated fatty acids (PUFAs) in vegetable oil are not desirable for biodiesel or food oil due to their lower oxidative stability. The oil from Idesia polycarpa fruit contains 65–80% (mol%) linoleic acid (C18:2). Therefore, development of Idesia polycarpa cultivars with low PUFAs is highly desirable for Idesia polycarpa oil quality. Fatty acid desaturase 2 (FAD2) is the key enzyme converting oleic acid (C18:1) to C18:2. We isolated four FAD2 homologs from the fruit of Idesia polycarpa. Yeast transformed with IpFAD2-1, IpFAD2-2 and IpFAD2-3 can generate appreciable amounts of hexadecadienoic acid (C16:2) and C18:2, which are not present in wild-type yeast cells, revealing that the proteins encoded by these genes have Δ12 desaturase activity. Only trace amounts of C18:2 and little C16:2 were detected in yeast cells transformed with IpFAD2-4, suggesting IpFAD2-4 displays low activity. We also analyzed the activity of several FAD2 natural variants of Idesia polycarpa in yeast and found that a highly conserved Gly376 substitution caused the markedly reduced products catalyzed by IpFAD2-3. This glycine is also essential for the activity of IpFAD2-1 and IpFAD2-2, but its replacement in other plant FAD2 proteins displays different effects on the desaturase activity, suggesting its distinct roles across plant FAD2s proteins.
Highlights
Vegetable oils are essential resources for nutritional applications, and for sustainable industrial feedstocks, which are commonly used in paints, lubricants, soaps, biodiesel, etc. [1,2]
Our previous study showed that four Fatty acid desaturase 2 (FAD2) orthologs are present in the fruit of Idesia polycarpa [5], which were renamed IpFAD2-1 (c63420_g2), IpFAD2-2 (c56614_g1), IpFAD2-3 (c63420_g1), and IpFAD2-4
The entire coding sequence (CDS) of IpFAD2-1, IpFAD2-2, IpFAD2-3, and IpFAD2-4 were cloned from Idesia ploycarpa
Summary
Vegetable oils are essential resources for nutritional applications, and for sustainable industrial feedstocks, which are commonly used in paints, lubricants, soaps, biodiesel, etc. [1,2]. The demand for vegetable oils is quickly increasing due to the fast growing population across the world. To meet this demand, many efforts have been made to improve the yields of oil crops or to domesticate wild oilseed plants [3]. It is receiving more attention due to the high amount of oil in its fruits, which can potentially be used in the biodiesel industry [4]. The oil from Idesia polycarpa fruit is healthy and edible since it contains 65–80% (mol%) linoleic acid (C18:2). It would be valuable to breed Idesia polycarpa cultivars which produce oils with low C18:2 and high C18:1 contents and it would be helpful to uncover the desaturation mechanism in woody plants
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