Diacylglycerol Acyltransferase1 Promotes Triacylglycerol Biosynthesis in Oil Tea ( Camellia oleifera ) Seeds through Transcriptional Activation by WRINKLED1

Camellia oil, a nutritionally rich edible oil derived from Camellia oleifera seeds, is predominantly stored as triacylglycerol (TAG) during fruit maturation. However, a limited understanding of the genetic and regulatory mechanisms governing Camellia oil accumulation has hindered efforts to optimize its yield. In this study, three C. oleifera diacylglycerol acyltransferase ( CoDGAT ) genes were identified and characterized, wherein CoDGAT1 emerged as the primary contributor to seed TAG biosynthesis, functioning within the endoplasmic reticulum and increasing seed oil content by 64.4% in transgenic plant. Through weighted gene coexpression network analysis, we identified WRINKLED1 (CoWRI1) as a candidate transcriptional regulator of CoDGAT1 . Both genes exhibited significant upregulation during seed maturation. Mechanistically, CoWRI1 activated CoDGAT1 by directly binding to AW-box motifs in its promoter, thereby promoting TAG accumulation. Additionally, CoWRI1 expression was suppressed by salicylic acid, methyl jasmonate, and darkness, suggesting that phytohormones and environmental signals modulate TAG accumulation through the WRI1- DGAT1 pathway. These findings provide an important basis for improving Camellia oil production through biotechnological manipulation of DGAT1 and WRI1 genes.