A tree peony INDETERMINATE DOMAIN transcription factor PrIDD7 inhibits seed oil accumulation.

PrIDD7 acts as a key negative regulator of tree peony seed oil accumulation by downregulating the FA biosynthesis genes PrHAD and PrKASII. Seed oils serve not only as a critical dietary source of nutrients but also as a key raw material for industrial manufacturing. However, the transcriptional regulatory mechanisms underlying seed oil accumulation remain largely unclear. The tree peony (Paeonia rockii) is characterized by high seed oil content and a high proportion of polyunsaturated fatty acids, which are essential for human health. Here, we identified a tree peony INDETERMINATE DOMAIN transcription factor, PrIDD7, that functions as an essential negative regulator of seed oil accumulation. Ectopic overexpression of PrIDD7 in both Nicotiana benthamiana leaves and Arabidopsis thaliana seeds significantly decreased oil content. In contrast, silencing PrIDD7 in tree peony seeds increased oil content, coincident with the upregulation of several genes that promote oil accumulation. Further transcriptional regulatory assays demonstrated that PrIDD7 inhibits seed oil accumulation by downregulating the FA biosynthesis genes HYDROXYACYL-ACP DEHYDRATASE and KETO-ACYL SYNTHASE II. These findings advance our understanding of the molecular basis of seed oil accumulation and provide a valuable target gene for improving oilseed crops.