WRINKLED1 transcription factor activates lipid biosynthesis to enhance oil accumulation in Pinus koraiensis

Pinus koraiensis is an economically important oil-producing conifer whose seeds are enriched in unsaturated fatty acids, exhibiting significant nutritional and industrial value. However, the molecular mechanisms underlying lipid biosynthesis in P. koraiensis remain largely unexplored, particularly regarding the role of transcription factors in seed oil accumulation. In this study, we identified and functionally characterized PkWRI1a, a homolog of WRINKLED1 (WRI1), a key transcription factor in the AP2/ERF family, as a pivotal regulator of lipid biosynthesis of P. koraiensis. PkWRI1a displayed tissue-specific expression, with transcript levels markedly increasing during seed maturation, coinciding with rapid triacylglycerol (TAG) accumulation. Overexpression of PkWRI1a in P. koraiensis calli significantly enhanced total lipid and TAG contents, accompanied by the upregulation of key genes involved in glycolysis, fatty acid biosynthesis, and the Kennedy pathway. Chromatin immunoprecipitation sequencing and dual-luciferase assays further demonstrated that PkWRI1a directly binds to promoters of lipid biosynthetic genes encoding critical enzymes, including palmitoyl-CoA hydrolase, glyceraldehyde-3-phosphate dehydrogenase, and phosphatidic acid phosphatase, thereby activating their transcription. Collectively, these findings provide novel insights into the transcriptional regulation of oil biosynthesis in P. koraiensis and highlight the potential of PkWRI1a as a promising target for the genetic enhancement of seed oil content in coniferous trees.