Comprehensive transcriptional variability analysis reveals gene networks regulating seed oil content of Brassica napus

The comprehensive regulatory network in seed oil biosynthesis

Plant oils play a crucial role in human nutrition, industrial applications and biofuel production. While the enzymes involved in fatty acid (FA) biosynthesis are well-studied, the regulatory networks governing these processes remain largely unexplored. This review explores the intricate regulatory networks modulating seed oil biosynthesis, focusing on key pathways and factors. Seed oil content is determined by the efficiency of de novo FA synthesis as well as influenced by sugar transport, lipid metabolism, FA synthesis inhibitors and fine-tuning mechanisms. At the center of this regulatory network is WRINKLED1 (WRI1), which plays a conserved role in promoting seed oil content across various plant species. WRI1 interacts with multiple proteins, and its expression level is regulated by upstream regulators, including members of the LAFL network. Beyond the LAFL network, we also discuss a potential nuclear factor-Y (NF-Y) regulatory network in soybean with an emphasis on NF-YA and NF-YB and their associated proteins. This NF-Y network represents a promising avenue for future efforts aimed at enhancing oil accumulation and improving stress tolerance in soybean. Additionally, the application of omics-based approaches is of great significance. Advances in omics technologies have greatly facilitated the identification of gene resources, opening new opportunities for genetic improvement. Importantly, several transcription factors involved in oil biosynthesis also participate in stress responses, highlighting a potential link between the two processes. This comprehensive review elucidates the complex mechanisms underlying the regulation of oil biosynthesis, offering insights into potential biotechnological strategies for improving oil production and stress tolerance in oil crops.

A rare dominant allele DYSOC1 determines seed coat color and improves seed oil content in Brassica napus

Yellow seed coat color (SCC) is a valuable trait in Brassica napus, which is significantly correlated to high seed oil content (SOC) and low seed lignocellulose content (SLC). However, no dominant yellow SCC genes were identified in B. napus. In this study, a dominant yellow SCC B. napus N53-2 was verified, and then 58,981 eQTLs and 25 trans-eQTL hotspots were identified in a double haploid population derived from N53-2 and black SCC material Ken-C8. A rare dominant allele DYSOC1 (dominant gene of yellow seed coat color and improved seed oil content 1) was subsequently cloned in a trans-eQTL hotspot that colocated with SCC, SOC, and SLC QTL hotspot on ChrA09 through QTL fine mapping and multi-omics analysis. Transgenic experiments revealed that the expression of DYSOC1 produced yellow SCC seeds with significantly increased SOC and decreased SLC. Our result provides a rare dominant yellow SCC allele in B. napus, which has excellent potential for yellow SCC and high SOC rapeseed breeding.

Increasing oil content in Brassica oilseed species

Brassica oilseed species are the third most important in the world, providing approximately 15 % of the total vegetable oils. Three species (Brassica rapa, B. juncea, B. napus) dominate with B. napus being the most common in Canada, China and Europe. Originally, B. napus was a crop producing seed with high erucic acid content, which still persists today, to some extent, and is used for industrial purposes. In contrast, cultivars which produce seed used for food and feed are low erucic acid cultivars which also have reduced glucosinolate content. Because of the limit to agricultural land, recent efforts have been made to increase productivity of oil crops, including Brassica oilseed species. In this article, we have detailed research in this regard. We have covered modern genetic, genomic and metabolic control analysis approaches to identifying potential targets for the manipulation of seed oil content. Details of work on the use of quantitative trait loci, genome-wide association and comparative functional genomics to highlight factors influencing seed oil accumulation are given and functional proteins which can affect this process are discussed. In summary, a wide variety of inputs are proving useful for the improvement of Brassica oilseed species, as major sources of global vegetable oil.

Genome-wide expression quantitative trait locus analysis reveals silk-preferential gene regulatory network in maize

Silk of maize (Zea mays L.) contains diverse metabolites with complicated structures and functions, making it a great challenge to explore the mechanisms of metabolic regulation. Genome-wide identification of silk-preferential genes and investigation of their expression regulation provide an opportunity to reveal the regulatory networks of metabolism. Here, we applied the expression quantitative trait locus (eQTL) mapping on a maize natural population to explore the regulation of gene expression in unpollinated silk of maize. We obtained 3,985 silk-preferential genes that were specifically or preferentially expressed in silk using our population. Silk-preferential genes showed more obvious expression variations compared with broadly expressed genes that were ubiquitously expressed in most tissues. We found that trans-eQTL regulation played a more important role for silk-preferential genes compared to the broadly expressed genes. The relationship between 38 transcription factors and 85 target genes, including silk-preferential genes, were detected. Finally, we constructed a transcriptional regulatory network around the silk-preferential gene Bx10, which was proposed to be associated with response to abiotic stress and biotic stress. Taken together, this study deepened our understanding of transcriptome variation in maize silk and the expression regulation of silk-preferential genes, enhancing the investigation of regulatory networks on metabolic pathways.

Functional genomics of Brassica napus: Progresses, challenges, and perspectives

Brassica napus, commonly known as rapeseed or canola, is a major oil crop contributing over 13% to the stable supply of edible vegetable oil worldwide. Identification and understanding the gene functions in the B. napus genome is crucial for genomic breeding. A group of genes controlling agronomic traits have been successfully cloned through functional genomics studies in B. napus. In this review, we present an overview of the progress made in the functional genomics of B. napus, including the availability of germplasm resources, omics databases and cloned functional genes. Based on the current progress, we also highlight the main challenges and perspectives in this field. The advances in the functional genomics of B. napus contribute to a better understanding of the genetic basis underlying the complex agronomic traits in B. napus and will expedite the breeding of high quality, high resistance and high yield in B. napus varieties.

GhL1L1 regulates the contents of unsaturated fatty acids by activating the expression of GhFAD2 genes in cotton

Edible oils with high unsaturated fatty acids, particularly oleic acid, are beneficial to human health. Cotton is one of the top five oil crops in the world, but the mechanism of high-quality oil synthesis and regulatory networks in cotton are largely unclear. Here, we identified Leafy cotyledon1-like 1 (GhL1L1), a NF-YB subfamily gene that is specifically expressed during somatic embryogenesis and seed maturation in cotton. Overexpression of GhL1L1 regulates the contents of unsaturated fatty acids in cotton, especially in the seeds, which is associated with altered expression of the cotton fatty acid biosynthesis-related genes. GhL1L1 synergistically enhanced the expression of GhFAD2-1A by binding to the G-box in its promoter, leading to an increase in the content of linoleic acid. Furthermore, this activation could be enhanced by GhNF-YC2 and GhNF-YA1 by form a transcriptional complex. Collectively, these results contribute to provide new insights into the molecular mechanism of oil biosynthesis in cotton and can facilitate genetic manipulation of cotton varieties with enhanced oil content.

Oil candidate genes in seeds of cotton (Gossypium hirsutum L.) and functional validation of GhPXN1

BACKGROUND

Cottonseed oil is a promising edible plant oil with abundant unsaturated fatty acids. However, few studies have been conducted to explore the characteristics of cottonseed oil. The molecular mechanism of cottonseed oil accumulation remains unclear.

RESULTS

In the present study, we conducted comparative transcriptome and weighted gene co-expression network (WGCNA) analysis for two G. hirsutum materials with significant difference in cottonseed oil content. Results showed that, between the high oil genotype 6053 (H6053) and the low oil genotype 2052 (L2052), a total of 412, 507, 1,121, 1,953, and 2,019 differentially expressed genes (DEGs) were detected at 10, 15, 20, 25, and 30 DPA, respectively. Remarkably, a large number of the down-regulated DEGs were enriched in the phenylalanine metabolic processes. Investigation into the dynamic changes of expression profiling of genes associated with both phenylalanine metabolism and oil biosynthesis has shed light on a significant competitive relationship in substrate allocation during cottonseed development. Additionally, the WGCNA analysis of all DEGs identified eight distinct modules, one of which includes GhPXN1, a gene closely associated with oil accumulation. Through phylogenetic analysis, we hypothesized that GhPXN1 in G. hirsutum might have been introgressed from G. arboreum. Overexpression of the GhPXN1 gene in tobacco leaf suggested a significant reduction in oil content compared to the empty-vector transformants. Furthermore, ten other crucial oil candidate genes identified in this study were also validated using quantitative real-time PCR (qRT-PCR).

CONCLUSIONS

Overall, this study enhances our comprehension of the molecular mechanisms underlying cottonseed oil accumulation.

Characterization of novel loci controlling seed oil content in Brassica napus by marker metabolite-based multi-omics analysis

BACKGROUND

Seed oil content is an important agronomic trait of Brassica napus (B. napus), and metabolites are considered as the bridge between genotype and phenotype for physical traits.

RESULTS

Using a widely targeted metabolomics analysis in a natural population of 388 B. napus inbred lines, we quantify 2172 metabolites in mature seeds by liquid chromatography mass spectrometry, in which 131 marker metabolites are identified to be correlated with seed oil content. These metabolites are then selected for further metabolite genome-wide association study and metabolite transcriptome-wide association study. Combined with weighted correlation network analysis, we construct a triple relationship network, which includes 21,000 edges and 4384 nodes among metabolites, metabolite quantitative trait loci, genes, and co-expression modules. We validate the function of BnaA03.TT4, BnaC02.TT4, and BnaC05.UK, three candidate genes predicted by multi-omics analysis, which show significant impacts on seed oil content through regulating flavonoid metabolism in B. napus.

CONCLUSIONS

This study demonstrates the advantage of utilizing marker metabolites integrated with multi-omics analysis to dissect the genetic basis of agronomic traits in crops.