A basic Leucine zipper transcription factor, AsbZIP26, positively regulates the synthesis of Alliin in garlic (Allium sativum L.)

• A transcription factor that regulates the synthesis of alliin has been identified. • AsbZIP26 can activate the expression of the AsFMO1 gene. • First elucidation of the molecular mechanism underlying alliin synthesis. Garlic is a significant medicinal and culinary plant, with its primary bioactive compound being alliin. The bZIP transcription factor is pivotal in plant secondary metabolism and growth, yet its function in garlic remains unexplored. The previously identified key enzyme gene, AsFMO1 in garlic, is known to directly regulate alliin synthesis, however, the specific molecular mechanism is still unknown. In this research, the transcription factor AsbZIP26 was discovered in the leaves of purple-skinned garlic in PiZhou, demonstrating a positive regulatory role in alliin biosynthesis. Transcriptomic data indicated that mechanical damage stress highly induced the expression of the AsbZIP26 gene, a favorable condition for alliin synthesis. Subcellular localization revealed nuclear targeting of AsbZIP26. Employing yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA) analysis, and chromatin immunoprecipitation (ChIP), it was confirmed that AsbZIP26 specifically binds to the G-box region of the AsFMO1 promoter, directly activating its expression and playing a crucial function in garlic biosynthesis. Overexpression of AsbZIP26 in garlic callus tissues resulted in increased alliin levels. Overall, this study discovered a functional transcription factor AsbZIP26 in garlic, which can regulate the synthesis of alliin in garlic, filling the gap in the alliin synthesis pathway and providing new ideas for garlic breeding and selection for improving garlic varieties.