Chimeric AGAMOUS repressor induces serrated petal phenotype in Torenia fournieri similar to that induced by cytokinin application

Abstract

The homeotic protein AGAMOUS (AG) terminates the floral meristem and promotes the development of stamens and carpels in Arabidopsis. Disruption of its function or expression of the chimeric AG repressor (AGSRDX) results in redundant petals, known as a double flower phenotype. To investigate whether this morphological change in Arabidopsis is applicable to ornamental flowers to increase their horticultural value, we introduced AGSRDX into torenia (Torenia fournieri Lind.) plants. Transgenic torenia plants expressing AGSRDX showed no redundancy in petal number, although they exhibited serration in petal margins, anthocyanin accumulation and morphological change in the stigma surface, and formation of extra vascular bundles in petals and styles. Anatomical observation of petals and styles revealed that these phenotypes are highly similar to those of forchlorfenuron (CPPU)-treated torenia plants especially in the derangement of vascular bundles. Phenotypes similar to AGSRDX transgenic torenia plants were also observed when the chimeric repressors for torenia C-function genes TfFAR or TfPLE1, homologs of Antirrhinum FARINELLI and PLENA respectively, were expressed. These results suggest that the morphological changes in AGSRDX transgenic torenia plants are induced by the disruption of C-function. These novel phenotypes might be caused by the modification of cytokinin-dependent regulation in vascular bundle formation and ectopic expression of the chimeric repressors in all whorls by the cauliflower mosaic virus (CaMV) 35S promoter.

Production of picotee-type flowers in Japanese gentian by CRES-T

“…This result was similar to a previous study in Arabidopsis where more than 90% suppression of the reporter gene was achieved (Hiratsu et al 2004). Recently, CRES-T was successfully applied to several horticultural plants including torenia (Narumi et al 2008; Sasaki et al in this issue), morning glory (Ono et al in this issue), and cyclamen (Tanaka et al in this issue). The EAR motif is conserved among a wide range of higher plant species, including Arabidopsis, rice, tobacco, petunia, and wheat (Ohta et al 2001).…”

“…In this system, a transcription factor is converted from activator into a repressor by fusion to the EAR motif (SRDX), and this repressor dominantly suppresses the expression of the target genes of the transcription factor (Hiratsu et al 2003). Suppression by CRES-T has been successful in a wide variety of monocots and dicots including Arabidopsis, torenia, morning glory, cyclamen, and rice (Mitsuda et al 2006;Narumi et al 2008; some articles in this special issue). Chimeric repressors have been applied to various transcription factors, including those that regulate morphological development: CUP SHAPED COTYLEDON1 (Hiratsu et al 2003), TCPs (Koyama et al 2007), AGAMOUS (Mitsuda et al 2006;Narumi et al 2008;Xu et al 2006) (Hiratsu et al 2003); and secondary wall formation: NSTs (Mitsuda et al 2007(Mitsuda et al , 2008.…”

“…Suppression by CRES-T has been successful in a wide variety of monocots and dicots including Arabidopsis, torenia, morning glory, cyclamen, and rice (Mitsuda et al 2006;Narumi et al 2008; some articles in this special issue). Chimeric repressors have been applied to various transcription factors, including those that regulate morphological development: CUP SHAPED COTYLEDON1 (Hiratsu et al 2003), TCPs (Koyama et al 2007), AGAMOUS (Mitsuda et al 2006;Narumi et al 2008;Xu et al 2006) (Hiratsu et al 2003); and secondary wall formation: NSTs (Mitsuda et al 2007(Mitsuda et al , 2008. In secondary metabolic biosynthesis, a chimeric repressor for PRODUCTION OF ANTHOCYANIN PIGMENT1 (PAP1), which is a positive regulator of phenylpropanoid biosynthesis in Arabidopsis, suppressed the accumulation of anthocyanin in transgenic Arabidopsis seedlings (Hiratsu et al 2003;Matsui et al 2004).…”

Torenia fournieri (torenia) as a model plant for transgenic studies

“…Recently, Narumi et al (2008) showed that a gene silencing technology targeting transcription factor, Chimeric REpressor gene-Silencing Technology (CRES-T; Hiratsu et al 2003), functioned in torenia. The CRES-T system could become a powerful tool for suppressing transcription factor genes in torenia.…”

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

“…Several of the transgenic plants created using the CRES-T system exhibited recognizable phenotypes and among these, the alteration of flower shape is particularly well-suited to experimental purposes Narumi et al 2008;Ohtsubo 2011). We used A. thaliana TFs for the CRES-T system because A. thaliana TFs are well studied compared with those of I. nil.…”