Promotion of Efficient Molecular Breeding Using Chimeric Repressors in Ornamental Flowers

Useful novel floral traits have recently been generated in various ornamental crops by using Chimeric REpressor gene Silencing Technology (CRES-T). CRES-T is a plant-specific gene silencing method that targets transcription factors (TFs), causing a dominant loss-of-function phenotype. In our group project, we applied CRES-T to various ornamental crops and mainly elucidated the following points: 1) CRES-T was effective for the modification of floral traits, 2) it was useful in higher polyploidy crops, and 3) it enabled the creation of commercially valuable flowers. In CRES-T, the attachment of a short repression domain derived from a transcriptional repressor to the C-terminal region of target TFs converts transcriptional activators to dominant chimeric repressors. In the target flower species, some Arabidopsis chimeric repressors were effective for the production of new floral traits without cloning the TF genes of interest. Therefore, the use of Arabidopsis chimeric repressors could be widely effective for many ornamental crops, even when the genome and/or expressed sequence tag (EST) information of target crops is unavailable or lacking. In addition, the collective transformation of chimeric repressors into ornamental crops is effective in isolating useful and/or target floral traits, such as petal colors, petal shapes, and color patterns. This technology could help to accelerate the developmental period and reduce the cost of developing new floral traits.