The bZIP transcription factor PrABI5 regulates α-linolenic acid synthesis in tree peony seeds

The tree peony (Paeonia rockii), a traditional ornamental plant in Chinese horticulture, has recently gained significant attention as a promising woody oil crop rich in α-linolenic acid (ALA), an omega-3 fatty acid with multiple industrial value and health benefits. The development of plant resources rich in ALA and the molecular mechanisms of plant ALA synthesis have emerged as research hotspots. We previously identified the key gene PrFAD3 encoding fatty acid desaturase, which catalyze linoleic acid (LA) to synthesis ALA. In P. rockii, however, the upstream transcriptional mechanism remained unclear. In this study, we disclosed that a bZIP family transcription factor, PrABI5, is involved in the synthesis of ALA in P. rockii seeds. Present research indicated that PrABI5 activates the expression of PrFAD3 by binding to the ABRE element in the promoter. We verified the positive role of PrABI5 in promoting ALA synthesis through gene overexpression and virus-induced gene silencing (VIGS). Additionally, PrABI5 enhances ALA biosynthesis by recruiting PrCAM7, a member of calmodulin protein family, to strengthen transcriptional regulation of the PrFAD3. Collectively, our study provides novel insights into the transcriptional mechanisms of ALA synthesis in plant seeds and the improvement of plant fatty acid composition through molecular biology techniques.