Parsley promoter displays higher activity than the CaMV 35S promoter and the chrysanthemum promoter for productive, constitutive, and durable expression of a transgene in .

The chrysanthemum () is one of the most popular ornamental plants in the world. Genetic transformation is a promising tool for improving traits, editing genomes, and studying plant physiology. Promoters are vital components for efficient transformation, determining the level, location, and timing of transgene expression. The cauliflower mosaic virus (CaMV) 35S promoter is most frequently used in dicotyledonous plants but is less efficient in chrysanthemums than in tobacco or torenia plants. Previously, we used the parsley () promoter in chrysanthemums for the first time and analyzed its activity in transgenic calli. To expand the variety of constitutive promoters in chrysanthemums, we cloned the upstream region of the () gene and compared its promoter activity with the 35S and promoters in several organs, as well as its durability for long-term cultivation. The promoter has higher activity than the 35S promoter in calli but is less durable. The promoter has the highest activity not only in calli but also in leaves, ray florets, and disk florets, and retains its activity after long-term cultivation. In conclusion, we have provided useful information and an additional type of promoter available for transgene expression in chrysanthemums.