FT Protein Research Articles

Comparative Genomic Analysis of PEBP Genes in Cucurbits Explores the Interactors of Cucumber CsPEBPs Related to Flowering Time.

The family of phosphatidylethanolamine-binding proteins (PEBPs) participates in various plant biological processes, mainly flowering regulation and seed germination. In cucurbit crops, several PEBP genes have been recognized to be responsible for flowering time. However, the investigation of PEBP family members across the genomes of cucurbit species has not been reported, and their conservation and divergence in structure and function remain largely unclear. Herein, PEBP genes were identified from seven cucurbit crops and were used to perform a comparative genomics analysis. The cucurbit PEBP proteins could be classified into MFT, FT, TFL, and PEBP clades, and further, the TFL clade was divided into BFT-like, CEN-like, and TFL1-like subclades. The MFT-like, FT-like, and TFL-like proteins were clearly distinguished by a critical amino acid residue at the 85th position of the Arabidopsis FT protein. In gene expression analysis, CsaPEBP1 was highly expressed in flowers, and its expression levels in females and males were 70.5 and 89.2 times higher, respectively, than those in leaves. CsaPEBP5, CsaPEBP6, and CsaPEBP7 were specifically expressed in male flowers, with expression levels 58.1, 17.3, and 15.7 times higher, respectively, than those of leaves. At least five CsaPEBP genes exhibited the highest expression during the later stages of corolla opening. Through clustering of time-series-based RNA-seq data, several potential transcription factors (TFs) interacting with four CsaPEBPs were identified during cucumber corolla opening. Because of the tandem repeats of binding sites in promoters, NF-YB (Csa4G037610) and GATA (Csa7G64580) TFs appeared to be better able to regulate the CsaPEBP2 and CsaPEBP5 genes, respectively. This study would provide helpful information for further investigating the roles of PEBP genes and their interacting TFs in growth and development processes, such as flowering time regulation in cucurbit crops.

Transcriptomic Analysis of Flowering Time Genes in Cultivated Chickpea and Wild Cicer.

Chickpea (Cicer arietinum L.) is a major grain legume and a good source of plant-based protein. However, comprehensive knowledge of flowering time control in Cicer is lacking. In this study, we acquire high-throughput transcriptome sequencing data and analyze changes in gene expression during floral transition in the early flowering cultivar ICCV 96029, later flowering C. arietinum accessions, and two wild species, C. reticulatum and C. echinospermum. We identify Cicer orthologs of A. thaliana flowering time genes and analyze differential expression of 278 genes between four species/accessions, three tissue types, and two conditions. Our results show that the differences in gene expression between ICCV 96029 and other cultivated chickpea accessions are vernalization-dependent. In addition, we highlight the role of FTa3, an ortholog of FLOWERING LOCUS T in Arabidopsis, in the vernalization response of cultivated chickpea. A common set of differentially expressed genes was found for all comparisons between wild species and cultivars. The direction of expression change for different copies of the FT-INTERACTING PROTEIN 1 gene was variable in different comparisons, which suggests complex mechanisms of FT protein transport. Our study makes a contribution to the understanding of flowering time control in Cicer, and can provide genetic strategies to further improve this important agronomic trait.

Efficiency of graft-transmitted JcFT for floral induction in woody perennial species of the Jatropha genus depends on transport distance

FLOWERING LOCUS T (FT) promotes flowering by integrating six genetic pathways. In Arabidopsis, the FT protein is transported from leaves to shoot apices and induces flowering. However, contradictory conclusions about floral induction via graft-transmitted FT in trees were reported in previous studies. We obtained extremely early-flowering transgenic woody Jatropha curcas L. by overexpression of J. curcas FT using Arabidopsis thaliana SUCROSE TRANSPORTER 2 (SUC2) promoter (SUC2:JcFT) and non-flowering transgenic J. curcas by RNA interference (RNAi), which were used to investigate the function of graft-transmitted JcFT in floral induction in woody perennials. Scions from five wild-type species of the Jatropha genus and from JcFT-RNAi transgenic J. curcas were grafted onto SUC2:JcFT rootstocks. Most grafted plants produced flowers in 1–2 months, and the flowering percentage and frequency of various grafted plants decreased with increasing scion length. Consistently, FT protein abundance in scions also decreased with increasing distance from graft junctions to the buds. These findings suggest that FT proteins can be transmitted by grafting and can induce the floral transition in woody perennials, and the efficiency of graft-transmitted JcFT for floral induction depends on the scion length, which may help explain previous seemingly contradictory observations regarding floral induction via graft-transmitted FT in trees.

Transient activity of the florigen complex during the floral transition in Arabidopsis thaliana.

FLOWERING LOCUS T (FT) is an essential component of florigen in Arabidopsis thaliana Transcription of FT is induced in leaves, and the resulting FT protein is transported to the shoot apex, in which it initiates floral development. Previous analyses suggest that, together with the b-ZIP transcription factor FD, FT regulates the transcription of downstream targets such as APETALA1 (AP1) in floral anlagen. However, conclusive in vivo evidence that FT is transported to the shoot apex to form an FT-FD complex is lacking. Here, using an innovative in vivo imaging technique, we show that the FT-FD complex and AP1 colocalise in floral anlagen. In addition, the FT-FD complex disappears soon after the floral transition owing to a reduction in FD transcripts in the shoot apex. We further show that misinduction of FD activity after the transition leads to defective reproductive development. Taken together, our results indicate that the FT-FD complex functions as a transient stimulus and imply that a regulatory mechanism exists during the floral transition that reduces FT-FD complex levels via modulation of FD expression.

Uncoupling FT Protein Transport from its Function.

Uncoupling FT Protein Transport from its Function.

Precision genome engineering through adenine base editing in plants.

The recent development of adenine base editors (ABEs) has enabled efficient and precise A-to-G base conversions in higher eukaryotic cells. Here, we show that plant-compatible ABE systems can be successfully applied to protoplasts of Arabidopsis thaliana and Brassica napus through transient transfection, and to individual plants through Agrobacterium-mediated transformation to obtain organisms with desired phenotypes. Targeted, precise A-to-G substitutions generated a single amino acid change in the FT protein or mis-splicing of the PDS3 RNA transcript, and we could thereby obtain transgenic plants with late-flowering and albino phenotypes, respectively. Our results provide 'proof of concept' for in planta ABE applications that can lead to induced neo-functionalization or altered mRNA splicing, opening up new avenues for plant genome engineering and biotechnology.

It was in 1936 when the existence of ‘florigen’ was initially predicted as a plant hormone that transmits information on daylight length at their leaves to the tip of the stem and stimulates flower initiation. In 2007, it was finally identified as a protein, which is coded by the FT gene in Arabidopsis thaliana. FT protein is produced in the

It was in 1936 when the existence of ‘florigen’ was initially predicted as a plant hormone that transmits information on daylight length at their leaves to the tip of the stem and stimulates flower initiation. In 2007, it was finally identified as a protein, which is coded by the <i>FT</i> gene in <i>Arabidopsis thaliana</i>. FT protein is produced in the

Arabidopsis florigen FT binds to diurnally oscillating phospholipids that accelerate flowering

Arabidopsis FT protein is a component of florigen, which transmits photoperiodic flowering signals from leaf companion cells to the shoot apex. Here, we show that FT specifically binds phosphatidylcholine (PC) in vitro. A transgenic approach to increase PC levels in vivo in the shoot meristem accelerates flowering whereas reduced PC levels delay flowering, demonstrating that PC levels are correlated with flowering time. The early flowering is related to FT activity, because expression of FT-effector genes is increased in these plants. Simultaneous increase of FT and PC in the shoot apical meristem further stimulates flowering, whereas a loss of FT function leads to an attenuation of the effect of increased PC. Specific molecular species of PC oscillate diurnally, and night-dominant species are not the preferred ligands of FT. Elevating night-dominant species during the day delays flowering. We suggest that FT binds to diurnally changing molecular species of PC to promote flowering.

Heavy traffic in the fast lane: long‐distance signalling by macromolecules

The two major vascular conduits in plants, the xylem and phloem, theoretically provide opportunities for the long-distance translocation of almost any type of water-borne molecule. This review focuses on the signalling functions conveyed by the movement of macromolecules. Here, a signal is defined as the communication of information from source to destination, where it modifies development, physiology or defence through altered gene expression or by direct influences on other cellular processes. Xylem and phloem sap both contain diverse classes of proteins; in addition, phloem contains many full-length and small RNA species. Only a few of these mobile molecules have proven functions in signalling. The transduction of signals typically depends on connection to appropriate signalling pathways. Incoming protein signals require specific detection systems, generally via receptors. Mobile RNAs require either the translation or presence of a homologous target. Given that phloem sieve elements are enucleate and lack translation machinery, RNA function requires subsequent unloading at least into adjacent companion cells. The binding of RNA by proteins in ribonucleoprotein complexes enables the translocation of some signals, with evidence for both sequence-specific and size-specific binding. Several examples of long-distance macromolecular signalling are highlighted, including the FT protein signal which regulates flowering time and other developmental switches.

Mobile signals in day length-regulated flowering: Gibberellins, flowering locus T, and sucrose

Despite low activity for stem growth, the gibberellins GA5 and GA6 act as long-day (LD) florigens in Lolium temulentum L. This claim is based on extensive evidence covering GA synthesis in LD in the induced leaf and their transport to the shoot apex where they act in a dose-dependent manner. GAs also act as a LD florigen in association with cold vernalization of L. perenne. In contrast, highly bioactive GA4 and, possibly, GA1 are important florigens in Arabidopsis thaliana (L.) Heynh. This species contrast reflects differences in GA deactivation, which is unimportant for Arabidopsis but dominant in L. temulentum. It is unclear if GAs participate in flowering responses of short-day (SD) species since it is LD, which up-regulate enzymes for GA biosynthesis. Sugars (sucrose) may also act directly as a florigen and, specifically, with increase in photosynthesis as in LD or when light intensity is increased in SD. In addition, in LD sucrose can indirectly cause flowering by up-regulating FT expression, the FT protein acting as a further leaf-to-apex transported florigen. Thus, there are not only multiple florigens but there can be complex interactions between the signaling pathways controlling production of these various florigens.

ZCN8 encodes a potential orthologue of Arabidopsis FT florigen that integrates both endogenous and photoperiod flowering signals in maize

Higher plants use multiple perceptive measures to coordinate flowering time with environmental and endogenous cues. Physiological studies show that florigen is a mobile factor that transmits floral inductive signals from the leaf to the shoot apex. Arabidopsis FT protein is widely regarded as the archetype florigen found in diverse plant species, particularly in plants that use inductive photoperiods to flower. Recently, a large family of FT homologues in maize, the Zea CENTRORADIALIS (ZCN) genes, was described, suggesting that maize also contains FT-related proteins that act as a florigen. The product of one member of this large family, ZCN8, has several attributes that make it a good candidate as a maize florigen. Mechanisms underlying the floral transition in maize are less well understood than those of other species, partly because flowering in temperate maize is dependent largely on endogenous signals. The maize indeterminate1 (id1) gene is an important regulator of maize autonomous flowering that acts in leaves to mediate the transmission or production of florigenic signals. This study finds that id1 acts upstream of ZCN8 to control its expression, suggesting a possible new link to flowering in day-neutral maize. Moreover, in teosinte, a tropical progenitor of maize that requires short-day photoperiods to induce flowering, ZCN8 is highly up-regulated in leaves under inductive photoperiods. Finally, vascular-specific expression of ZCN8 in Arabidopsis complements the ft-1 mutation, demonstrating that leaf-specific expression of ZCN8 can induce flowering. These results suggest that ZCN8 may encode a florigen that integrates both endogenous and environmental signals in maize.

The alleles at the E1 locus impact the expression pattern of two soybean FT-like genes shown to induce flowering in Arabidopsis

A small gene family of phosphatidyl ethanolamine-binding proteins (PEBP) has been shown to function as key regulators in flowering; in Arabidopsis thaliana the FT protein promotes flowering whilst the closely related TFL1 protein represses flowering. Control of flowering time in soybean [Glycine max (L.) Merrill] is important for geographic adaptation and maximizing yield. Soybean breeders have identified a series of loci, the E-genes, that control photoperiod-mediated flowering time, yet how these loci control flowering is poorly understood. The objectives of this study were to evaluate the expression of GmFT-like genes in the E1 near-isogenic line (NIL) background. Of the 20 closely related PEBP proteins in the soybean genome, ten are similar to the Arabidopsis FT protein. Expression analysis of these ten GmFT-like genes confirmed that only two are detectable in the conditions tested. Further analysis of these two genes in the E1 NILs grown under short-day (SD) and long-day (LD) conditions showed a diurnal expression and tissue specificity expression commensurate with soybean flowering time under SD and LD conditions, suggesting that these were good candidates for flowering induction in soybean. Arabidopsis ft mutant lines flowered early when transformed with the two soybean genes, suggesting that the soybean genes can complement the Arabidopsis FT function. Flowering time in E1 NILs is consistent with the differential expression of the two GmFT-like genes under SD and LD conditions, suggesting that the E1 locus, at least in part, impacts time to flowering through the regulation of soybean FT expression.

Developing a method for customized induction of flowering

BackgroundThe ability to induce flowering on demand is of significant biotechnological interest. FT protein has been recently identified as an important component of the mobile flowering hormone, florigen, whose function is conserved across the plant kingdom. We therefore focused on manipulation of both endogenous and heterologous FT genes to develop a floral induction system where flowering would be inhibited until it was induced on demand. The concept was tested in the model plant Arabidopsis thaliana (Arabidopsis).ResultsOur starting point was plants with strongly delayed flowering due to silencing of FT with an artificial microRNA directed at FT (amiR-FT) [1]. First, we showed that constitutive expression of a heterologous FT gene (FTa1), from the model legume Medicago truncatula, (Medicago) was able to rescue the amiR-FT late-flowering phenotype. In order to induce flowering in a controlled way, the FTa1 gene was then expressed under the control of an alcohol-inducible promoter in the late flowering amiR-FT plants. Upon exposure to ethanol, FTa1 was rapidly up regulated and this resulted in the synchronous induction of flowering.ConclusionsWe have thus demonstrated a controlled-inducible flowering system using a novel combination of endogenous and heterologous FT genes. The universal florigenic nature of FT suggests that this type of system should be applicable to crops of economic value where flowering control is desirable.

TheFT-LikeZCN8Gene Functions as a Floral Activator and Is Involved in Photoperiod Sensitivity in Maize

The mobile floral-promoting signal, florigen, is thought to consist of, in part, the FT protein named after the Arabidopsis thaliana gene FLOWERING LOCUS T. FT is transcribed and translated in leaves and its protein moves via the phloem to the shoot apical meristem where it promotes the transition from vegetative to reproductive development. In our search for a maize FT-like floral activator(s), seven Zea mays CENTRORADIALIS (ZCN) genes encoding FT homologous proteins were studied. ZCN8 stood out as the only ZCN having the requisite characteristics for possessing florigenic activity. In photoperiod sensitive tropical lines, ZCN8 transcripts were strongly upregulated in a diurnal manner under floral-inductive short days. In day-neutral temperate lines, ZCN8 mRNA level was independent of daylength and displayed only a weak cycling pattern. ZCN8 is normally expressed in leaf phloem, but ectopic expression of ZCN8 in vegetative stage shoot apices induced early flowering in transgenic plants. Silencing of ZCN8 by artificial microRNA resulted in late flowering. ZCN8 was placed downstream of indeterminate1 and upstream of delayed flowering1, two other floral activator genes. We propose a flowering model linking photoperiod sensitivity of tropical maize to diurnal regulation of ZCN8.

シロイヌナズナのフロリゲン FT 蛋白質の長距離伝達性の解析

シロイヌナズナのフロリゲン FT 蛋白質の長距離伝達性の解析

Structure and function of plants

I was really pleased to have been given the opportunity to review this book. After all, structure and function is the aspect of botany closest to my own interests. So, anticipating some sort of modern-day version of Haberlandt's famous Physiological plant anatomy text, it was with great expectation that I opened MacAdam's book and explored the contents. The book's first five chapters – The Plant Cell; Plant Meristems and Tissues; Plant Roots; Plant Stems; and Plant Leaves and Translocation – are fine; you can see a definite ‘structure’ theme to these topics. In particular, in Chapter 5 you can feel a marked integration of structure and its functional dimension. However, the remaining nine chapters go far beyond the structure–function theme and is the main issue I have with the book. It is not the structure–function text its title led me to expect; instead it is a general botany text. Whilst there is nothing wrong with that, the onus must be upon the author/publisher to make it clear that this is the case – a better title would go a long way towards achieving that. Accordingly, the remaining chapters deal with the general botanical topics of: Reproduction in Flowering Plants; Plant Nutrition; Plant Water Relations; Macromolecules and Enzyme Activity; Photosynthesis; Respiration; Environmental Regulation of Plant Development; Hormonal Regulation of Plant Development; and Secondary Plant Products. The book is completed with an 18-page glossary; a reference section (a mix of very up-to-date ones, and other much older – ‘classic’? – ones, but on balance too few); and ten pages of index. One aspect of the book deserving of comment concerns the illustrations. On the plus side, abundant colour is used throughout, which I liked, and illustrations are numerous and of a good size to be seen clearly. However, it seems strange nowadays that a plant cell (Fig. 1.1), a mitochondrion (Fig. 1.13 – whose cristae are unlabelled and appear misleadingly as blobs free in the matrix) and a chloroplast (Fig. 1.14) should be illustrated solely by diagrams. Surely, suitably labelled TEM images could have been used? From an accuracy point of view some of the legends are in need of amendment. For instance, Fig. 6.12 shows an Antirrhinum inflorescence, but is labelled as foxglove in the legend. However, there is a bigger issue with Fig. 4.17, which shows bark of ‘sycamore’ yet is described as Platanus. The term ‘sycamore’ in the UK refers to Acer pseudoplatanus (a maple); whereas in North America sycamore refers to trees of the genus Platanus (known as plane trees in Europe). Proof of the value of using unambiguous scientific names, and a cautionary tale for publishers of books designed to have international appeal – many commonly-used terms do not travel far beyond national borders. In terms of topicality, the book appears up-to-date; e.g. it includes aquaporins, molecular motors and the identification of florigen as FT protein, but coverage is a little patchy in places. For example, the Hormonal Regulation chapter provides a good introductory-level summary of the ‘classical’ five plant growth regulators yet does not mention salicyclic acid, jasmonates or brassinolides. Elsewhere the book goes into great depth about historic aspects of some topics at the expense of dealing with matters of more pressing concern. For example, it provides a nice summary of the discovery of the biochemistry of photosynthesis; however, at over three pages this seems a luxury – especially so when topical subjects such as plant response to stress, climate change and biotic interactions are hardly covered at all. Also, ranging from very detailed and advanced considerations of factors influencing the balance between photosynthesis and photorespiration to the different types of flower arrangement, yet claiming to be ‘for introductory students … and plant enthusiasts’, I wonder if the book is clear on its intended audience and whether it serves their interests fully without perhaps intimidating them. Given that we now know this is a general botany text, almost any other plant biology textbook is a competitor. But if we limit consideration to the book's intended audience – which the publisher advises us is ‘undergraduates, faculty, extension faculty, and members of Master Gardener programs’, then it does its job reasonably well. Structure and function will withstand scrutiny alongside Capon (2005) and Ingram et al. (2008) as an introductory-level text: it would not fare so well against more substantial textbooks such as Smith et al. (2009 – see the following review, below), which are aimed at more advanced or specialist students. On balance, providing you are aware that this is a general plant biology text – largely aimed at an introductory level – you will find much of value here.

MiR156-Regulated SPL Transcription Factors Define an Endogenous Flowering Pathway in Arabidopsis thaliana

The FT gene integrates several external and endogenous cues controlling flowering, including information on day length. A complex of the mobile FT protein and the bZIP transcription factor FD in turn has a central role in activating genes that execute the switch from vegetative to reproductive development. Here we reveal that microRNA156-targeted SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes not only act downstream of FT/FD, but also define a separate endogenous flowering pathway. High levels of miR156 in young plants prevent precocious flowering. A subsequent day length-independent decline in miR156 abundance provides a permissive environment for flowering and is paralleled by a rise in SPL levels. At the shoot apex, FT/FD and SPLs converge on an overlapping set of targets, with SPLs directly activating flower-promoting MADS box genes, providing a molecular substrate for both the redundant activities and the feed-forward action of the miR156/SPL and FT/FD modules in flowering control.

Plant research accelerates along the (bio)informatics superhighway

The Keystone Symposium on Plant Sensing, Response and Adaptation to the Environment took place between 11 and 16 January 2009, at Big Sky, Montana, USA, and was organized by S.A. Kay & J. Chory. ![][1] See Glossary for abbreviations used in this article In spite of the fanfare surrounding the two‐hundredth anniversary of the birth of Charles Darwin, and the one‐hundred and fiftieth anniversary of his most celebrated book ‘ On the Origin of Species ’ (Darwin, 1859), many people would still be surprised to learn that Darwin wrote a nearly 600 page book entitled ‘ The Power of Movement in Plants ’ (Darwin, 1880). As most plants have their location fixed as soon as their roots enter the soil, non‐specialists might wonder how much movement plants can make. However, movement is not limited to locomotion, and many of the movements studied by Darwin probably evolved in response to the unique challenges imposed by the rooted habit. Unable to change location, plants have developed exquisite abilities to sense, respond to and adapt to their local environment. One example that captured Darwin's attention is the navigation of the radicle (root) tip through the complex soil environment to optimize water and nutrient acquisition. He stated, “It is hardly an exaggeration to say that the tip of the radicle thus endowed, and having the power of directing the movements of the adjoining parts, acts like the brain of one of the lower animals[…].” These root‐growth movements were but one of many environmental responses discussed by plant biologists gathered at the recent Keystone Symposium on Plant Sensing, Response and Adaptation to the Environment. Root growth is controlled by gravity, water and nutrient acquisition; whereas growth of the aerial shoot is regulated primarily by the light environment. Various photoreceptors allow plants to judge light intensity, direction … [1]: /embed/graphic-1.gif

The 14-3-3 Protein GF14c Acts as a Negative Regulator of Flowering in Rice by Interacting with the Florigen Hd3a

Hd3a and FT proteins have recently been proposed to act as florigens in rice and Arabidopsis, respectively; however, the molecular mechanisms of their function remain to be determined. In this study, we identified GF14c (a 14-3-3 protein) as an Hd3a-interacting protein in a yeast two-hybrid screen. In vitro and in vivo experiments, using a combination of pull-down assays and bimolecular fluorescence complementation, confirmed the interaction between Hd3a and GF14c. Functional analysis using either GF14c overexpression or knockout transgenic rice plants indicated that this interaction plays a role in the regulation of flowering. GF14c-overexpressing plants exhibited a delay in flowering and the knockout mutants displayed early flowering relative to the wild-type plants under short-day conditions. These results suggest that GF14c acts as a negative regulator of flowering by interacting with Hd3a. Since the 14-3-3 protein has been shown to interact with FT protein in tomato and Arabidopsis, our results in rice provide important findings about FT signaling in plants.

Phloem transport of flowering signals

Seasonal variability in environmental parameters such as day length regulates many aspects of plant development. The transition from vegetative growth to flowering in Arabidopsis is regulated by seasonal changes in day length through a genetically defined molecular cascade known as the photoperiod pathway. Recent advances were made in understanding the tissues in which different components of the photoperiod pathway act to regulate floral induction. These studies highlighted the key role of the FT protein, which is produced in the leaves in response to inductive day lengths and traffics through the phloem to initiate flowering at the shoot apex. Unveiling the cellular and molecular details of this systemic signaling process will be required for a complete understanding of flowering regulation and other photoperiodic processes.