Overexpression of HANABA TARANU in cultivated strawberry delays flowering and leads to defective flower and fruit development

Cultivated strawberry is one of the most important horticultural crops in the world, and the fruit yields and economic benefits are largely dependent on the quality of floral initiation and floral organ development. However, the underlying regulatory mechanisms controlling these processes in strawberry are largely unknown. In this study, the function of a GATA transcription factor gene, HANABA TARANU (HAN), in floral initiation and floral organ development was characterized in strawberry. FaHAN is expressed in four whorls of the floral organs. Overexpression (OE) of FaHAN in the strawberry cultivar ‘Benihoppe’ delayed flowering by at least one week by affecting key genes, such as TERMINAL FLOWER 1, APETALA 1…and increased the number of runners. FaHAN-OE plants also showed malformed floral organs, especially the deformed stigmas with disordered arrangement. Several key genes for pistil apical development such as STYLISH, YUCCA 1, and auxin-related genes such as GH3.5, PIN-FORMED 1, which play important roles in pistil primordium development in many plant species, were all down-regulated in FaHAN-OE plants. Further observations showed that the fruit deformity rate was nearly 4-fold higher than in control plants. Together, this study provides a new approach for exploring floral initiation and floral organ development in strawberry.