Arabidopsis chimeric TCP3 repressor produces novel floral traits in Torenia fournieri and Chrysanthemum morifolium

Abstract

Shape and color are the most important characteristics of ornamental flowers, and the generation of the novel phenotypes has been pursued in the breeding. Distinct floral morphology such as fringed petals and double flowers has been selected preferentially in the breeding of horticultural crops from wild species.Transcription factors control the expression of multiple genes and act as the master regulator of various phenotypes. Most of the floral morphological changes in Arabidopsis reported until date are attributed to the dysfunction in transcription factors (Ferrario et al. 2004;Jack 2004;. Knockout or knockdown of transcription factor genes is therefore efficient for the functional analysis of genes and creation of novel plant phenotypes. Although RNA interference (RNAi) effectively knocks down the expression of targeted genes in model plants such as Arabidopsis and rice, it is difficult to apply this technology to horticultural plants with limited genomic sequence information and polyploid genomes because of unavailability of target sequences and genetic redundancy which is often accompanied by sequence variability.CRES-T is a unique gene-silencing method utilizing plant-specific chimeric transcriptional repressors. These chimeric repressors are produced from transcription factors by fusing a transcriptional repression domain SRDX (Hiratsu et al. 2002). This modification converts many transcription factors into strong transcriptional repressors. Chimeric repressors dominantly suppress the expression of respective target genes and confer loss-offunction phenotypes at high frequency, even in the presence of functionally redundant transcriptional activators in Arabidopsis and rice (Hiratsu et al. 2003;Koyama et al. 2007Koyama et al. , 2010Matsui et al. 2004Matsui et al. , 2005 Arabidopsis chimeric TCP3 repressor produces novel floral traits in Torenia fournieri and Chrysanthemum morifolium Abstract Chimeric REpressor gene-Silencing Technology (CRES-T) is a powerful gene-silencing tool to analyze the function of Arabidopsis transcription factors. To investigate whether CRES-T is also applicable to horticultural plants inadequate for genetic engineering because of their limited molecular biological characterization and polyploidy, we applied CRES-T to torenia and the hexaploid chrysanthemum and produced their transgenic plants expressing the chimeric repressor derived from the Arabidopsis TEOSINTE BRANCHED1, CYCLOIDEA, and PCF family transcription factor 3 (TCP3) fused with a plant-specific transcriptional repression domain named SRDX, consisting of 12 amino acids originated from the EAR-motif (TCP3-SRDX). Transgenic torenia and chrysanthemum expressing TCP3-SRDX exhibited fringed leaves and short pistils, while those expressing TCP3 fused with either the mutated repression domain (TCP3-mSRDX) or the overexpressor of TCP3 (TCP3-ox) did not exhibit phenotypic changes. In addition to fringed leaves, TCP3-SRDX transgenic torenia plants exhibited petals with fringed margins, distinctive color patterns, and reduce...

Beyond the blue rose: Modification of floral architecture with plant-specific chimeric repressors

“…As a consequence, these two transcription genes were chosen to provide suggestive and contrasting results. All the flowers transformed with chimeric TCP-related repressors exhibited similar morphological changes, such as serrated margins of the vegetative tissues and unique petal color patterns (Gion et al 2011;Narumi et al 2011;Tanaka et al 2011aTanaka et al , 2011b. In addition, we confirmed that repressive activity occurs only when the chimeric repressor has an intact repression domain, using diploid torenia and hexaploid chrysanthemum .…”

The new FioreDB database provides comprehensive information on plant transcription factors and phenotypes induced by CRES-T in ornamental and model plants

“…Representative results are summarized in Table 2. The TEOSINTE BRANCHED1, CYCLOIDEA and PCF (TCP) TFs induced the expected phenotypes in most examined species even when the Arabidopsis gene was employed (Table 2) (Gion et al 2011;Narumi et al 2011;Tanaka et al 2011), while the Arabidopsis MADS box TFs, such as AGAMOUS (AG) and APETALA3 (AP3), did not induce the expected phenotypes in plants other than Arabidopsis (Table 2). However, as shown for morning glory, when orthologs of the MADS box TFs from each species was employed, the expected phenotypes were induced (Table 2) (Sage-Ono et al 2011).…”

Promotion of Efficient Molecular Breeding Using Chimeric Repressors in Ornamental Flowers

“…In addition, SRDX is effective for many ornamental crops, such as Torenia, rose, gentian, lisianthus, cyclamen, chrysanthemum, and morning glory (Mitsuda et al 2008, Mitsuda et al 2011a. Because this system functions dominantly, the chimeric repressors even worked in higher polyploidy plants, such as the hexaploid chrysanthemum (Mitsuda et al 2011a, Narumi et al 2011. It is noteworthy that chimeric repressors constructed with Arabidopsis TFs frequently worked in other ornamental crops for the functional analysis of TFs and the development of novel floral traits without any further modification (Narumi et al 2011, Shikata et al 2011, Gion et al 2011.…”

“…Because this system functions dominantly, the chimeric repressors even worked in higher polyploidy plants, such as the hexaploid chrysanthemum (Mitsuda et al 2011a, Narumi et al 2011. It is noteworthy that chimeric repressors constructed with Arabidopsis TFs frequently worked in other ornamental crops for the functional analysis of TFs and the development of novel floral traits without any further modification (Narumi et al 2011, Shikata et al 2011, Gion et al 2011. Information regarding the floral phenotypes generated in the CRES-T project is available on the FioreDB website: Database for Flower Bio-engineering by CRES-T (Mitsuda et al 2011a; http://www.cres-t.org/fiore/public_db/index.…”