Abstract
In many higher plants, seed oil accumulation is governed by complex multilevel regulatory networks including transcriptional regulation, which primarily affects fatty acid biosynthesis. Tree peony (Paeonia rockii), a perennial deciduous shrub endemic to China is notable for its seed oil that is abundant in unsaturated fatty acids. We discovered that a tree peony trihelix transcription factor, PrASIL1, localized in the nucleus, is expressed predominantly in developing seeds during maturation. Ectopic overexpression of PrASIL1 in Nicotiana benthamiana leaf tissue and Arabidopsis thaliana seeds significantly reduced total fatty acids and altered the fatty acid composition. These changes were in turn associated with the decreased expression of multitudinous genes involved in plastidial fatty acid synthesis and oil accumulation. Thus, we inferred that PrASIL1 is a critical transcription factor that represses oil accumulation by down-regulating numerous key genes during seed oil biosynthesis. In contrary, up-regulation of oil biosynthesis genes and a significant increase in total lipids and several major fatty acids were observed in PrASIL1-silenced tree peony leaves. Together, these results provide insights into the role of trihelix transcription factor PrASIL1 in controlling seed oil accumulation. PrASIL1 can be targeted potentially for oil enhancement in tree peony and other crops through gene manipulation.
Highlights
In many higher plants, the seed storage reserves include oils as triacylglycerols (TAGs), carbohydrates, and storage proteins
Transcriptomics revealed that a trihelix transcription factors (TFs) PrASIL1 of tree peony was highly expressed in the early and late stages of seed development suggesting its association with seedrelated traits (Figure 1A)
To identify the genes regulated by PrASIL1 in Arabidopsis, we examined the expression of various FA and TAG biosynthesis genes in seeds by Quantitative RT-PCR (qRT-PCR)
Summary
The seed storage reserves include oils as triacylglycerols (TAGs), carbohydrates, and storage proteins. A novel FA synthesis repressor, TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR4, was investigated to inhibit the expression of fatty acid biosynthetic genes by interacting with WRI1 These finding is of great importance for advancing the study of transcriptional regulatory networks of seed oil accumulation (Duan et al, 2017; Li et al, 2017; Kong et al, 2020a). We show that PrASIL1 acts as a negative regulator and its reduced expression is associated with upregulation of oil biosynthesis genes and oil accumulation in seeds until maturation in tree peony. 2-year-old seedlings at 4 weeks post-germination were selected for virus-induced gene silencing (VIGS) Both plants, Nicotiana benthamiana for transient expression studies and Arabidopsis thaliana (Columbia0; wild type) for ectopic overexpression experiment were grown in the same climate chamber with 16h light/8h dark and 65% relative humidity at 22◦C. The primers used for RT-PCR and qRT-PCR are listed in Supplementary Table 2
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