The ARF Family Transcription Factor PrARF9 Positively Affects Fatty Acid Accumulation in Paeonia rockii

Fatty acids play critical roles in plant growth and stress adaptation, primarily through modulating membrane fluidity. This study combined bioinformatics (genome-wide identification and chromosomal localization) with experimental techniques (RT-qPCR, VIGS, and GC) to investigate the ARF family in Paeonia rockii. Seventeen PrARF genes were identified, showing evolutionary collinearity with Arabidopsis thaliana and Vitis vinifera and uneven chromosomal distribution. Among these, PrARF9 was specifically and highly expressed during late seed development, exhibiting a pattern highly consistent with the fatty acid synthesis key gene PrFAD3 and the accumulation trend of α-linolenic acid (ALA). In Nicotiana benthamiana, transient overexpression of PrARF9 upregulated its homologous gene NbFAD3, resulting in increased total fatty acid content and elevated lipid droplet accumulation. In contrast, in Paeonia rockii, silencing of PrARF9 downregulated PrFAD3 expression and reduced fatty acid levels, whereas overexpression of PrARF9 produced the opposite effect. We present a comprehensive analysis of the ARF gene family in P. rockii, combined with functional verification of a candidate gene regulating lipid synthesis. In summary, PrARF9 positively regulates PrFAD3, thereby participating in oil accumulation and ALA synthesis in P. rockii.