The trihelix transcription factor PrASR3 regulates α-linolenic acid accumulation in tree peony seeds

α-Linolenic acid (ALA) is an omega-3 polyunsaturated fatty acid (FA) that is essential for human health and is obtained mainly from plant-sourced foods. The tree peony (Paeonia rockii) is a woody oilseed plant with high nutritional value, as its seed oil is rich in ALA. Previously, we found that tree peony phospholipid diacylglycerol acyltransferase 2 (PrPDAT2) plays an important role in seed oil ALA accumulation. However, the transcriptional mechanism by which PrPDAT2 promotes ALA accumulation in seed oils remains incompletely understood. Here, we identify a novel tree peony trihelix transcription factor (TF), PrASR3, that acts as a repressor of ALA accumulation in the seed by directly inhibiting PrPDAT2 transcription. Furthermore, our findings also show that the overexpression of PrASR3 in Nicotiana benthamiana leaves and Arabidopsis thaliana seeds alters FA composition. Silencing of PrASR3 in P. rockii seeds resulted in enhanced PrPDAT2 expression and ALA accumulation. In addition, we further demonstrated that the TEOSINTE BRANCHED 1/CYCLOIDEA/PCF (TCP) TF PrTCP14 interacts with PrASR3 to attenuate the inhibitory effect of PrASR3 on seed ALA accumulation. Overall, these findings enrich insight into the molecular regulatory mechanism of ALA accumulation in plants and provide a novel target for oil quality improvement in oilseed plants.