Characterization and functional analysis of novel α-bisabolol synthase (MrBAS) promoter from Matricaria recutita

Matricaria recutita is widely used in industry and as a medicinal plant because it contains α-bisabolol. Alpha-bisabolol has broad application prospects due to its healthy function and medical value. The activity of the α-bisabolol synthase (MrBAS) promoter determines the expression of the MrBAS gene, which in turn influences the synthesis and accumulation of α-bisabolol. However, the activity and tissue specificity of the MrBAS promoter have not yet been characterized. In this study, a 1327-base pair (bp) region upstream of the MrBAS of the translation start site was cloned from the genome of M. recutita. MrBAS promoter sequence analysis revealed multiple light-responsive elements, and further dark treatment reduced α-bisabolol content in flowers. The α-bisabolol content and MrBAS expression levels in various flower tissues showed a strong correlation. The 5' deletion analysis revealed that the MrBAS promoter sequence could drive β-glucuronidase (GUS) gene expression in Nicotiana benthamiana leaves, with activity decreasing as the fragment shortened. Transgenic experiments demonstrated that the MrBAS promoter could specifically drive GUS gene expression in Arabidopsis anthers, pollen tubes, and petals. Thus, the MrBAS promoter has the potential to be a tool for directing transgene expression specifically in flower organs, offering new research avenues for cultivar development.