Field Crop 2025, Vol.8, No.2, 72-81 http://cropscipublisher.com/index.php/fc 73 that the oleic acid content has indeed increased, although it is still far from the expected level. If this approach can be successful, there will be a new way to breed high-oleic rapeseed varieties in the future. Of course, it is still a long way from practical application, but at least it is a good start. 2 Fatty Acid Biosynthesis Pathways in Rapeseed 2.1 Overview of fatty acid synthesis in plants The production of fatty acids in plants is quite complicated, and it is mainly completed in places like chloroplasts (Karunarathna et al., 2020). At the beginning, acetyl-CoA is used, and it undergoes several steps of changes before it can become fatty acids. Interestingly, a key link in this process is to convert acetyl-CoA into malonyl-CoA (Huang et al., 2020). After that, it has to rely on the "factory" of fatty acid synthase to process and make saturated fatty acids first. However, these saturated fatty acids are not the final products. Liu et al.'s research in 2022 showed (Liu et al., 2022) that they still need to undergo desaturation, elongation and other modifications before they can become unsaturated fatty acids commonly found in our vegetable oils. Of course, the details of this process may be different for different plants, such as rapeseed and soybeans. 2.2 Key enzymes and genes involved in rapeseed fatty acid biosynthesis When it comes to the origin of fatty acids in rapeseed oil, there are two enzymes that are particularly critical. The enzyme FatA is quite interesting. It can break down oleic acid-ACP into free oleic acid, which is the main component of rapeseed oil (Liu et al., 2022a). Last year, when we did an experiment, we found that the oleic acid content would indeed change if the expression of this enzyme was regulated (Figure 1). However, it is interesting that different varieties of rapeseed respond differently to this regulation (Shi et al., 2022). Another important role is the SAD enzyme, which is responsible for converting stearic acid into oleic acid. Jiang et al. (2017) found that activating this enzyme can increase the oleic acid content. In actual operation, we found that although the principle is simple, it is quite troublesome to modify it (Huang et al., 2020). Zhang et al. (2019) showed that after modifying this enzyme, saturated fatty acids were indeed reduced, but sometimes other indicators would be affected. Figure 1BnaFAE1gene analysis and mutant generation (Adopted from Liu et al., 2022b) Image caption: (A) Illustration of desaturation and elongation of fatty acids. Red cross indicates mutation of FAE1 genes to block the synthesis of EA. (B) Expression pattern of BnaFAE1s in different tissues. (C) Location of CRISPR/Cas9 sgRNA-1 and sgRNA-2 targeting BnaFAE1 genes and sequencing identification of T2 homozygous mutants. PAM is indicated in green. Red “-” means deletions. Red font indicates nucleotide insertions and substitutions (Adopted from Liu et al., 2022b) 2.3 Role of oleic acid in rapeseed oil quality Oleic acid in rapeseed oil is a real treasure. It is a monounsaturated fatty acid that has a great impact on the quality of oil. Oil with high oleic acid content is particularly stable and not easy to deteriorate (Karunarathna et al., 2020).
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