Ectopic expression of EuWRI1, encoding a transcription factor in E. ulmoides, changes the seeds oil content in transgenic tobacco

The molecular mechanism of WRINKLED1 transcription factor regulating oil accumulation in developing seeds of castor bean

The transcription factor WRINKLED1 (WRI1), a member of AP2 gene family that contain typical AP2 domains, has been considered as a master regulator regulating oil biosynthesis in oilseeds. However, the regulatory mechanism of RcWRI1 in regulating oil accumulation during seed development has not been clearly addressed. Castor bean (Ricinus communis) is one of the most important non-edible oil crops and its seed oils are rich in hydroxy fatty acids, widely applied in industry. In this study, based on castor bean reference genome, three RcWRIs genes (RcWRI1, RcWRI2 and RcWRI3) were identified and the expressed association of RcWRI1 with oil accumulation were determined. Heterologous transformation of RcWRI1 significantly increased oil content in tobacco leaf, confirming that RcWRI1 activate lipid biosynthesis pathway. Using DNA Affinity Purification sequencing (DAP-seq) technology, we confirmed RcWRI1 binding with Transcription Start Site of genes and identified 7961 WRI1-binding candidate genes. Functionally, these identified genes were mainly involved in diverse metabolism pathways (including lipid biosynthesis). Three cis-elements AW-box ([CnTnG](n)7[CG]) and AW-boxes like ([GnAnC](n)6[GC]/[GnAnC](n)7[G]) bound with RcWRI1 were identified. Co-expression network analysis of RcWRI1 further found that RcWRI1 might be widely involved in biosynthesis of storage materials during seed development. In particular, yeast one hybrid experiments found that both AP2 domains within RcWRI1 were required in binding targeted genes. These results not only provide new evidence to understand the regulatory mechanism of RcWRI1 in regulation of oil accumulation during castor bean seed development, but also give candidate gene resource for subsequent genetic improvement toward increasing oil content in oilseed crops.

Chemical Composition of Tobacco Seed Oils and Their Antioxidant, Anti-Inflammatory, and Whitening Activities

Tobacco seeds are a valuable food oil resource, and tobacco seed oil is rich in nutrients, especially polyunsaturated fatty acids. The aim of this work was to perform a comprehensive study on the chemical constituents, and the antioxidant, anti-inflammatory, and whitening activities of tobacco seed oils (NC89 and BS4). A GC/MS analysis revealed that NC89 and BS4 had 11 and 6 volatile compounds, respectively. The PUFA contents in NC89 and BS4 were 74.98% and 72.84%, respectively. These two tobacco seed oils also presented good radical scavenging capacities with the neutralization of ABTS, OH^-, and superoxide (O₂^-) radicals in a concentration-dependent manner. Meanwhile, NC89 and BS4 inhibited reactive oxygen species (ROS) accumulation and cell apoptosis, enhanced SOD and CAT activities, and increased the GSH content in H₂O₂-induced HepG2 cells. In addition, NC89 and BS4 exhibited significant anti-inflammatory activities by inhibiting the expressions of NO, TNF-α, IL-1β, and IL-6 in LPS-induced RAW.264.7 cells through the regulation of the MAPK signaling pathway. Moreover, NC89 and BS4 expressed whitening activities by inhibiting tyrosinase activity and intracellular melanin production. Therefore, tobacco seed oils could be used as an important oil resource for the development of high value-added products.