Utilization of a floral organ-expressing AP1 promoter for generation of new floral traits in Torenia fournieri Lind

Abstract

To establish an efficient way to create novel floral traits in horticultural flowers, we have introduced many chimeric repressors of Arabidopsis transcription factors into torenia. Among them, we found a transgenic torenia exhibiting unopened flower buds and glossy dark green leaves with curled margins as a consequence of overexpression of Arabidopsis MYB24 with a transcriptional repression domain (MYB24-SRDX). Petals inside the flower buds exhibited a distinct coloration pattern. To bring out this favorable petal trait without inducing the unfavorable phenotypes due to the constitutive expression of chimeric repressors by the cauliflower mosaic virus 35S (35S) promoter, we tested the ability of a floral organ-specific Arabidopsis APETALA1 (AP1) promoter, which was found to be active in both petals and flower buds of torenia. As expected, AP1 pro:MYB24-SRDX transgenic torenias resulted in the opening of flowers and a normal leaf phenotype. Furthermore, these AP1 pro:MYB24-SRDX torenias exhibited wavy petals with a characteristic configuration. This is a good example of the utilization of a floral organ-specific promoter for creating distinct flower phenotypes without causing unfavorable morphological and physiological changes in other organs.