Morphological changes in Ipomoea nil using chimeric repressors of Arabidopsis TCP3 and TCP5

Chimeric REpressor gene-Silencing Technology (CRES-T) is a reverse genetic method that converts transcriptional factors (TFs) to chimeric repressors by fusion with an ethylene-responsive element-binding factor (ERF)-associated amphiphilic repression domain. The plant expressing chimeric repressor is expected to show loss-of-function phenotype of the original TF even in the presence of other functionally redundant TFs. We used the CRES-T system for modification of flower shape in transgenic Ipomoea nil (formally Pharbitis nil). I. nil is emerging as a model plant for ornamental flowers because it has produced a wide variety of historical mutants, and it has been chosen to be a part of the National BioResource Project in Japan. We used cDNAs of TFs of Arabidopsis thaliana with the CRES-T system because A. thaliana TFs are well characterized compared with I. nil TFs. For this study, we selected two TCP (TEOSINTE BRANCHED1, CYCLOIDEA, and PCF) TFs, TCP3 and TCP5, because overexpression of these chimeric repressors TCP3SRDX and TCP5SRDX causes severe morphological alterations in A. thaliana. We found that these chimeric repressors cause morphological alterations, an undeveloped corolla and wavy petals in I. nil. In addition, the sympetalous corolla was easily disrupted to form choripetalous corolla. Although several TCP3SRDX transgenic ornamental flowers were reported, typical sympetalous flowers like I. nil have not yet been presented.