Photoperiodic floral induction has had a significant impact on the agricultural and horticultural industries. Changes in day length are perceived in leaves, which synthesize systemic flowering inducers (florigens) and inhibitors (antiflorigens) that determine floral initiation at the shoot apex. Recently, FLOWERING LOCUS T (FT) was found to be a florigen; however, the identity of the corresponding antiflorigen remains to be elucidated. Here, we report the identification of an antiflorigen gene, Anti-florigenic FT/TFL1 family protein (AFT), from a wild chrysanthemum (Chrysanthemum seticuspe) whose expression is mainly induced in leaves under noninductive conditions. Gain-and loss-of-function analyses demonstrated that CsAFT acts systemically to inhibit flowering and plays a predominant role in the obligate photoperiodic response. A transient gene expression assay indicated that CsAFT inhibits flowering by directly antagonizing the flower-inductive activity of CsFTL3, a C. seticuspe ortholog of FT, through interaction with CsFDL1, a basic leucine zipper (bZIP) transcription factor FD homolog of Arabidopsis. Induction of CsAFT was triggered by the coincidence of phytochrome signals with the photosensitive phase set by the dusk signal; flowering occurred only when night length exceeded the photosensitive phase for CsAFT induction. Thus, the gated antiflorigen production system, a phytochrome-mediated response to light, determines obligate photoperiodic flowering response in chrysanthemums, which enables their year-round commercial production by artificial lighting. T he transition from the vegetative to the reproductive phase is one of the most important developmental stages in the plant life cycle. The timing of flowering during the year, which is an important adaptive trait that strongly influences reproductive fitness, is affected by both endogenous and environmental factors. Changes in day length (photoperiod) are among the most important and reliable seasonal signals to plants to reproduce at favorable times of the year. In 1920, Garner and Allard (1) demonstrated that several plant species flower in response to changes in day length and described this phenomenon as "photoperiodism." Plants are classified according to their photoperiodic responses as short-day plants (SDP), in which flowering occurs when the night length is longer than a critical minimum, long-day plants (LDP), in which flowering occurs when the day becomes longer than some crucial length, and day-neutral plants.Within the SDP and LDP, there are obligate (qualitative) and facultative (quantitative) types of photoperiodic responses. Obligate-type plants are those in which a particular photoperiod is an absolute requirement for the occurrence of a response. Chrysanthemum has become one of the most important horticultural crops since the discovery of photoperiodism because the flowering time of this obligate SDP can be strictly controlled by the use of blackouts or artificial lighting, day-length extension, or illumination during the middle of the...

Chrysanthemum is a typical short-day (SD) plant that responds to shortening daylength during the transition from the vegetative to the reproductive phase. FLOWERING LOCUS T (FT)/Heading date 3a (Hd3a) plays a pivotal role in the induction of phase transition and is proposed to encode a florigen. Three FT-like genes were isolated from Chrysanthemum seticuspe (Maxim.) Hand.-Mazz. f. boreale (Makino) H. Ohashi & Yonek, a wild diploid chrysanthemum: CsFTL1, CsFTL2, and CsFTL3. The organ-specific expression patterns of the three genes were similar: they were all expressed mainly in the leaves. However, their response to daylength differed in that under SD (floral-inductive) conditions, the expression of CsFTL1 and CsFTL2 was down-regulated, whereas that of CsFTL3 was up-regulated. CsFTL3 had the potential to induce early flowering since its overexpression in chrysanthemum could induce flowering under non-inductive conditions. CsFTL3-dependent graft-transmissible signals partially substituted for SD stimuli in chrysanthemum. The CsFTL3 expression levels in the two C. seticuspe accessions that differed in their critical daylengths for flowering closely coincided with the flowering response. The CsFTL3 expression levels in the leaves were higher under floral-inductive photoperiods than under non-inductive conditions in both the accessions, with the induction of floral integrator and/or floral meristem identity genes occurring in the shoot apexes. Taken together, these results indicate that the gene product of CsFTL3 is a key regulator of photoperiodic flowering in chrysanthemums.

We study concentrated binary colloidal suspensions, a model system which has a glass transition as the volume fraction φ of particles is increased. We use confocal microscopy to directly observe particle motion within dense samples with φ ranging from 0.4 to 0.7. Our binary mixtures have a particle diameter ratio d S /d L = 1/1.3 and particle number ratio N S /N L = 1.56, which are chosen to inhibit crystallization and enable long-time observations. Near the glass transition we find that particle dynamics are heterogeneous in both space and time. The most mobile particles occur in spatially localized groups. The length scales characterizing these mobile regions grow slightly as the glass transition is approached, with the largest length scales seen being ∼ 4 small particle diameters. We also study temporal fluctuations using the dynamic susceptibility χ 4 , and find that the fluctuations grow as the glass transition is approached. Analysis of both spatial and temporal dynamical heterogeneity show that the smaller species play an important role in facilitating particle rearrangements. The glass transition in our sample occurs at φ g ≈ 0.58, with characteristic signs of aging observed for all samples with φ > φ g .

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...

Flower colors and shapes are important commercial characters in floricultural plants. Many flowers with novel floral traits have been generated by crossfertilization, selective breeding, and mutation breeding (Shibata 2008). However, such traditional breeding methods require enormous time and effort. In contrast, genetic engineering in molecular breeding enables production of novel floral traits in floricultural plants that cannot be obtained by traditional breeding more efficiently and with less effort. For instance, attempts have been made for centuries to produce blue roses by traditional breeding, but this has proved impossible because roses lack a key enzyme, flavonoid 3Ј,5Ј-hydoxylase (F3Ј5ЈH), for delphinidin biosynthesis necessary for blue pigmentation. Katsumoto et al. (2007) succeeded in producing a delphinidin-accumulating rose with color that was blue-hued because of viola F3Ј5ЈH gene expression. Flower colors in carnation, petunia, torenia, and gentian have been modified by manipulating flavonoid biosynthesis genes (Nishihara and Nakatsuka 2010; Tanaka et al. 2009). Suppression by antisense gene or RNAi methods and overexpression by sense genes are typical strategies to manipulate genes of interest. However, information on DNA sequences is required for these strategies and genomic or EST analyses are still to be performed for most floricultural plants. On Abstract Molecular breeding with genetic modification enables the production of novel floral traits in floricultural plants that could not be obtained by traditional breeding. To facilitate novel flower production, we collectively introduced 2 sets of 42 and 50 chimeric repressors of Arabidopsis transcription factors into Agrobacterium and then used these to co-transform torenia (Torenia fournieri). We generated 750 transgenic torenias, and identification of the transgenes revealed that more than 80% of the transgenic torenias had a single transgene. A total of 264 plants showed phenotypic modification, and 91.2% displayed modified flower colors and/or shapes, such as altered color patterns, curled petal margins, and wavy petals. These results indicated that the collective transformation system can be applied to molecular breeding of flowers. Detailed analysis of the phenotypes revealed that PETAL LOSS could control blotch sizes and that modification of cell shape could change the texture of petals. We found that the chimeric repressors of functionally unknown transcription factors also induced novel floral traits, and therefore, the transgenic torenias provide an understanding of the functions of transcription factors that could not be revealed by previous studies in Arabidopsis.