Background Olive ( Olea europaea L.) oil accumulate more diacylglycerols (DAG) than mostly vegetable oils. Unsaturated fatty acids-enriched DAG consumption enhanced wellness in subjects. However, the mechanism of DAG accumulation is not yet fully understood. Methods In this study, gene network of DAG accumulation and fatty acid composition in the two olive mesocarps (“Chenggu 32” (CG) and “Koroneiki” (QJ)) were investigated by integrating lipidome and transcriptome techniques. Results A total of 1,408 lipid molecules were identified by lipidomic analysis in olive mesocarp, of which DAG (DAG36:3, DAG36:4 and DAG36:5) showed higher content, and triacylglycerols (TAG54:3, TAG54:4) exhibited opposite trend in CG. Specifically, DAG was rich in polyunsaturated fatty acids (especially C18:2) at the sn-2 position, which was inconsistent with TAG at the same positions (Primarily C18:1). Transcriptomic analysis revealed that phospholipase C (NPC, EC 3.1.4.3) were up-regulated relative to QJ, whereas diacylglycerol kinase (ATP) (DGK, EC 2.7.1.107), diacylglycerol acyltransferase (DGAT, EC 2.3.1.20), and phospholipid: diacylglycerol acyltransferase (PDAT, EC 2.3.1.158) were down-regulated. Conclusion We speculated that the non-acyl coenzyme A pathway played a significant role in DAG biosynthesis. Additionally, fatty acyl-ACP thioesterase B (FATB, EC 3.1.2.14), stearoyl [acyl-carrier-protein] 9-desaturase (SAD, EC 1.14.19.2) and omega-6 fatty acid desaturase (FAD2, EC 1.14.19.6) were highly expressed in CG and may be involved in regulating fatty acid composition. Meanwhile, phospholipase A1 (LCAT, EC 3.1.1.32) involved in the acyl editing reaction facilitated PUFA linkage at the sn-2 position of DAG. Our findings provide novel insights to increase the DAG content, improve the fatty acid composition of olive oil, and identify candidate genes for the production of DAG-rich oils.

In this work, integrated transcriptome and proteome to offer a new insight of the molecular mechanisms linked to the nutritional quality of Koroneiki and Chenggu-32 by RNA sequencing and 4D Label-free quantitative proteomics technology. Physical and chemical properties studies showed that the main nutrient content of Koroneiki was significantly higher than Chenggu-32, proved the quality of Koroneiki was better. Compared to Koroneiki, there were differences in expression levels of 10,115 genes and 723 proteins in Chenggu-32, mainly related to enzymes in lipid metabolism and lipid biosynthesis. Through the joint analysis of transcriptome and proteome, it was found that the differentially expressed genes and differentially expressed proteins on the association were mainly enriched in starch and sucrose metabolism and α-linolenic acid metabolism pathways, indicated that the nutritional quality of olive fruits was related to the two metabolic pathways. The results of this study identified key genes and proteins related to nutrient metabolism and accumulation in olive fruits, provided transcriptomic and proteomic information for the molecular mechanism of nutritional changes in olive fruit, it helps to develop higher quality olive trees.

Macadamia nuts are an abundant source of the monounsaturated fats (59 %), oleic (50 %-65 %) and palmitoleic acid (12 %-30 %). As macadamia is generally an outcrossing species, this study focuses on the effect of both the maternal (seed parent) and paternal (pollen parent) genotype on the accumulation of the principal fatty acids in macadamia using a controlled 3 x 3 pollination trial. Both the seed parent and pollen parent were observed to significantly impact the fatty acid profile of macadamia nut kernels. In addition, the general combining abilities (GCA) of the parental cultivars and specific combining abilities (SCA) of parental crosses were determined, as well as identifying maternal/paternal combinations that could significantly increase palmitoleic acid and oleic acid, or decrease saturated fat concentration. These results provide evidence for the first time that pollen source has a significant impact on the fatty acid profile of macadamia kernels, and that previous reporting of the fatty acid profiles of macadamia cultivars is likely to be variable, due to the unknown genotype of pollen sources.

Macadamia nuts are an abundant source of monounsaturated fats which exhibit beneficial biological functions and reduce the risk of chronic disease. This study focuses on investigating the fatty acid profile of 197 diverse accessions of macadamia, across cultivars, wild accessions, and three Macadamia species. Macadamia accessions with potential enhanced nutritional value were identified, with eight promising lines detected. The interrelationship of C16:0, C18:0, C18:1, trans-C18:1 fatty acids was determined, and two possible biosynthetic pathways proposed: (1) a previously unidentified C16:0 desaturase is responsible for the desaturation of C16:0 and C18:0 desaturase is responsible for the desaturation of C18:0, with the former being less efficient, and: (2) C18:0 desaturase is responsible for desaturation of both C16:0 and C18:0, but shows weaker specificity towards C16:0. Further, timing of upregulation of C16:0 elongase during kernel development could further modify the fatty acid profile, by reducing the amount of C16:0 substrate available for desaturation.

Palmitoleic acid is an unusual omega-7 monounsaturated fatty acid that occurs naturally in high levels in macadamia plants. Due to its wide public acceptance and being a commonly occurring food, macadamia nuts may serve as an important dietary agent for the delivery of palmitoleic acid to the human body. This review focuses on discussing the biological functions of palmitoleic acid, the association of palmitoleic acid with various diseases, as well as the anticipated biosynthetic pathway of palmitoleic acid in macadamia plants. In addition, given the importance to regulate palmitoleic acid contents in macadamia to achieve improved nutrition and commercial value, this review also proposes GWAS as an effective strategy to identify the candidate genes responsible for the accumulation of palmitoleic acid in macadamia nuts.