## 3 Results and Discussion
### Analysis of RNA-Seq of Embryo Rice During Storage
#### 3.3.2 Changes in Gene Expression Related to Lipid Metabolism  
Through the accumulation of data in the early stage of the experiment, it can be found that lipid has a strong influence on the deterioration in rice during storage, and most of the formed volatile compounds are also caused by fatty acid changes [54]. Subsequently, lipid formation and metabolism were mainly analyzed to find the key factors affecting the storage of embryonic rice (Figure 7). It is mainly divided into two transcription processes, the green box for fatty acid biosynthesis and the yellow box for linoleic acid metabolism. In the biosynthesis of fatty acids, there are 11 DEGs (_ACSL_, _fadD_, _ACAA1_, _MF2_, _ACOX1_, _FabF_, _FabG_, _FabZ_, _FabI_, _MECR_, _FATB_). Acetyl-CoA is the starting material of fatty acid synthesis, and the _FabF_ gene indirectly regulates the distribution of acetyl-CoA-derived fatty acid products by the catalysis of the fatty acid chain extension. _FabF_ works synergistically with other enzymes (e.g., _FabG_, _FabZ_, _FabI_) to determine the length and saturation of the fatty acid chain. At 4 \({}^{\circ}\)C, the activity of the _FabF_ gene is inhibited, and the feedback inhibition is weak, while at 25 \({}^{\circ}\)C, the accumulation of fatty acids increases, and the feedback inhibition is stronger, resulting in the downregulation of _FabF_ expression. The _FabG_ gene encodes \(\beta\)-ketoacyl-ACP reductase. This enzyme is the first reductase in the fatty acid synthesis cycle, and its activity determines the amount of \(\beta\)-hydroxyl-ACP production, which in turn affects the final yield of fatty acids in subsequent reactions. The _FabZ_ gene encodes \(\beta\)-hydroxyl-ACP dehydration, and the _FabI_ gene encodes enoyl-ACP reductase, which enables the fatty acid synthesis cycle to proceed smoothly to the next stage of reaction. The activity and specificity of _FabI_ enzymes have an important effect on the saturation of fatty acids. In embryo rice, changes in its activity may lead to changes in the ratio of saturated and unsaturated fatty acids. The activity of _MECR_ directly affects the production of branched-chain fatty acids. If the expression of _MECR_ is upregulated, the synthesis of branched-chain fatty acids increases, which may change the composition of fatty acids in the rice. The _FATB_ gene encodes Acyl-ACP thioesterase B, which is responsible for the termination step of fatty acid synthesis, releasing mature fatty acids. The more fatty acids that are produced, the higher the fatty acid value (Figure 1A). Palmitic acid, as a fatty acid, is regulated by enzymes encoded by _ACSL_ and _fadD_ genes during the storage of embryonic rice, and its expression changes can be used as a molecular index to evaluate the storage stability of embryonic rice. It is significantly downregulated at 25 \({}^{\circ}\)C and significantly upregulated at 4 \({}^{\circ}\)C.  
In the metabolism of linoleic acid, acetyl-CoA (acetyl-CoA), as a precursor, participates in the synthesis of fatty acids, and the generated linoleic acid is further combined with glycerol diester through the CDP-choline pathway to form lecithin, which constitutes the main phospholipid component of the cell membrane [55]. There were 10 DEGs involved in linoleic acid metabolism. Lecithin is metabolized by _TGL4_ in three steps: \(\alpha\)-linolenic acid, linoleicate, and arachid. The generation of \(\alpha\)-linolenic acid also requires the action of _LCAT3_[56]. _LOX_ further breaks down polyunsaturated fatty acids (such as linoleic acid and linolenic acid) into malondialdehydedehyde by oxidizing them, triggering a chain reaction that leads to rancidity [57], nutrient loss, and odor.