Integrated transcriptome and proteome analysis the molecular mechanisms of nutritional quality in 'Chenggu-32' and 'Koroneiki' olives fruits (Olea europaea L.)

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.

Integrated lipidomic and transcriptomic analysis reveals diacylglycerol accumulation in olive of Longnan (China)

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.

Comprehensive Evaluation of Quality of Camellia semiserrata Seed Oils from Various Harvest Dates

The ripening degree of camellia fruit is one of the key factors affecting the quality of camellia seed oil. In this study, taking Camellia semiserrata as the research object, the oil content, physicochemical indexes, nutritional indexes, fatty acid composition, and volatile compounds of camellia seed oils from various harvest dates (from September to October) were determined. The results showed that with the increase of the ripening degree of camellia fruit, the oil content of camellia seed increased at first and then decreased and reached the highest (58.74%) on September 30, while the acid value, peroxide value, β-sitosterol, α-tocopherol, and polyphenols of camellia seed oil showed a downward trend. Among them, the highest contents of β-sitosterol, α-tocopherol, and polyphenols were observed on September 2, which were 6881.60, 311.34, and 78.08 mg/kg, respectively. In terms of the fatty acid composition of camellia seed oils, the content of oleic acid increased at first and then decreased, the content of linoleic acid and palmitic acid decreased gradually, while the content of stearic acid increased gradually. A total of 37 volatile compounds were identified in different samples, including 12 aldehydes, 5 ketones, 12 alcohols, 2 acids, 5 esters, and 1 other. With the increase of the ripening degree, the concentration of aldehydes and alcohols increased at first and then decreased, the concentration of ketones and esters decreased gradually, but the concentration of acid compounds had no obvious rule. In addition, the camellia seed oils from various harvest dates were classified and comprehensively evaluated by principal component analysis and grey relation analysis. The results showed that different camellia seed oils could be divided into three groups, and the comprehensive score of camellia seed oils on September 30 was the highest. In general, this work can provide theoretical guidance for the harvest date of Camellia semiserrata.