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Background: Strong artificial and natural selection causes the formation of highly conserved haplotypes that harbor agronomically important genes. GWAS combination with haplotype analysis has evolved as an effective method to dissect the genetic architecture of complex traits in crop species., Results: We used the 60 K Brassica Infinium SNP array to perform a genome-wide analysis of haplotype blocks associated with oleic acid (C18:1) in rapeseed. Six haplotype regions were identified as significantly associated with oleic acid (C18:1) that mapped to chromosomes A02, A07, A08, C01, C02, and C03. Additionally, whole-genome sequencing of 50 rapeseed accessions revealed three genes (BnmtACP2-A02, BnABCI13-A02 and BnECI1-A02) in the A02 chromosome haplotype region and two genes (BnFAD8-C02 and BnSDP1-C02) in the C02 chromosome haplotype region that were closely linked to oleic acid content phenotypic variation. Moreover, the co-expression network analysis uncovered candidate genes from these two different haplotype regions with potential regulatory interrelationships with oleic acid content accumulation., Conclusions: Our results suggest that several candidate genes are closely linked, which provides us with an opportunity to develop functional haplotype markers for the improvement of the oleic acid content in rapeseed.

In China, the high-oleic acid rapeseed has an oil content of ∼42% and oleic acid (18:1) content of ∼80%. Compared to ordinary rapeseed, high-oleic acid rapeseed has higher levels of monounsaturated fatty acids and lower levels of saturated fatty acid and polyunsaturated fatty acids, and thus is of high nutritional and health value. In addition, high-oleic acid rapeseed oil imparts cardiovascular protective effects. Based on these properties, high-oleic acid oil crops have been extensively investigated and cultivated. We previously identified a CCCH-type transcription factor (BnZFP1, GenBank accession number XM_013796508) that is associated with high oleic acid traits from a Brassica napus subtractive hybridization library. In the present study, we overexpressed and silenced the BnZFP1 gene of B. napus. BnZFP1-overexpressing plants exhibited an 18.8% increase in oleic acid levels and a 3.8% increase in oil content. However, BNZFP1-silenced plants showed a 4.5% decrease in oleic acid levels, whereas no significant change in oil content was observed. Microarray and pull-down assays indicated that BnZFP1 has a total of thirty potential target genes. Further analysis and validation of one of the potential target genes, namely, diacylglycerol O-acyltransferases 1 (DGAT1) gene, indicated that it is positively regulated by BnZFP1. We also observed a correlation between elevated DGAT1 gene expression levels and higher oil content and oleic acid levels in rapeseed., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Simple Summary: The quality of rapeseed (Brassica napus) oil depends mainly on the degree of hydrocarbon chain saturation of fatty acids. In previous studies, seeds of the B. napus near-isogenic lines were used as raw materials by iTRAQ analysis at 20–35 days after pollination, and three differential proteins related to oleic acid metabolisms were found to be related to acetylation modification. Thus, we analyzed lysine acetylation using the same raw materials. The function of the corresponding genes of fatty acid metabolisms-related differential proteins was verified by identifying the overexpression of BnACP363K, BnACP363R, and BnACP363 in Arabidopsis thaliana. The results show that the acetylation modification of BnaACP3 may have a selective effect on oleic acid and slow down the conversion of oleic acid to linoleic acid. This is the first report of oleic acid synthesis regulation by acetylation. In this study, lysine acetylation analysis was conducted using two Brassica napus near-isogenic lines, HOCR and LOCR, containing high and low oleic acid contents, respectively, to explore this relationship. Proteins showing differences in quantitative information between the B. napus lines were identified in lysine acetylation analysis, and KEGG pathways were analyzed, yielding 45 enriched proteins, most of which are involved in carbon fixation in photosynthetic organisms, photosynthesis, ascorbate and aldarate metabolism, and glycolysis. Potential key genes related to fatty acid metabolisms were determined. To further explore the effect of acetylation modification on fatty acid metabolisms, the acyl-ACP3 related gene BnaACP363K was cloned, and a base mutation at No.63 was changed via overlapping primer PCR method. This study is the first to demonstrate that acetylation modification can regulate oleic acid metabolisms, which provides a promising approach for the study of the molecular mechanism of oleic acid in rapeseed. [ABSTRACT FROM AUTHOR]

High-oleic acid rapeseed is a new and promising rapeseed variety because it produces oil with high-quality health and nutrient properties. To identify differentially expressed proteins in a high-oleic acid rapeseed line, self-bred seeds (20 to 35 days after pollination) of a high- and a low-oleic acid rapeseed near-isogenic line (oleic acid contents of 81.4 and 56.2%, respectively) were used as raw materials for iTRAQ (isobaric tags for relative and absolute quantitation) analysis. In total, 24,755 peptides, 14,455 unique peptides, and 4726 proteins were identified. Among them, 137 differentially expressed proteins were assigned pathway annotations, accounting for 3.84% of the total proteins (3568). Three differentially expressed proteins, PSaB (gi|383930478), Lhcb6 (gi|50313237), and ALD (gi|15227981) were subjected to western blotting analyses. The results were consistent with the iTRAQ data, demonstrating the satisfactory quality of the iTRAQ experimental procedures and data. The transcript levels of 19 genes involved in fatty acid metabolism and photosynthesis were analyzed by qPCR. The transcript levels were consistent with the protein levels for 10 of these genes, but inconsistent for the other nine genes. Among the differentially expressed proteins were key enzymes in fatty acid biosynthesis and polyunsaturated fatty acid biosynthesis (acyl-CoA thioesterase, 3-ketoacyl-CoA reductase, omega 6 reductase, and acyl-CoA dehydrogenase), oleic acid biosynthesis (acyl-CoA thioesterase and omega 6 reductase), and seed lipid content (long-chain acyl-CoA synthetase). These results provide fundamental functional proteomics information for further breeding work on high-oleic acid rapeseed. This information will also be useful for research on the molecular mechanism of oleic acid synthesis. [ABSTRACT FROM AUTHOR]