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

• Published in: Plant diversity 2023-07, Vol.45 (4), p.469-478
• Main Authors: Tan, Qing, Han, Bing, Haque, Mohammad Enamul, Li, Ye-Lan, Wang, Yue, Wu, Di, Wu, Shi-Bo, Liu, Ai-Zhong
• Format: Article
• Language: English
• Subjects: Research Paper
• ISSN: 2468-2659; 2096-2703; 2468-2659
• DOI: 10.1016/j.pld.2022.09.003

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. • It is the first time used DAP-seq to comprehensively identify the binding sites and target genes of RcWRI1 at the genomic level. • The analysis of co-expression network and DAP-seq indicated that WRI1 have the ability to bind AW-box or AW-box like domain to regulate the lipid genes. • Yeast one-hybrid and tobacco transient activation experiments further demonstrated that the specific two AP2 domains co-determine the function of RcWRI1 in regulating transcription of lipid genes.