Terminal Flower Research Articles

Antisense Expression of Apple TFL1-like Gene (MdTFL1) Promotes Early Flowering and Causes Phenotypic Changes in Tobacco

Apples (Malus × domestica Borkh.) require up to several years for flowering and bearing fruits. The transition from vegetative to reproductive phase is controlled by floral regulators such as TERMINAL FLOWER 1 (TFL1) and FLOWERING LOCUS T (FT). TFL1 mediates the maintenance of vegetative phase, unlike the antagonistic function of FT to promote the transition into reproductive phase. In this study, we isolated apple TFL1-like gene (MdTFL1) to elucidate various phenotypic traits triggered by the antisense expression of MdTFL1 in tobacco apart from its floral induction function. Early flowering was observed in the tobacco line with MdTFL1 knockout, indicating the reduced time for transition to vegetative phases. Quantitative reverse-transcription PCR showed upregulation of genes involved in the regulation of floral induction, including NtAP1, NtSOC1, NFL1, and NtFTs, and downregulation of carotenoid cleavage dioxygenases (CCDs) and CEN-like genes in transgenic lines. Interestingly, transgenic tobacco expressing antisense MdTFL1 exhibited distinct morphological changes in lateral shoot outgrowth, internode length, and the development of leaves, flowers, and fruits. The results suggested that using the antisense expression of MdTFL1 gene is one of the approaches to shorten the vegetable phase and proposed improvement of plant architecture in horticultural crops.

MdGRF11, a growth-regulating factor, participates in the regulation of flowering time and interacts with MdTFL1/MdFT1 in apple

GROWTH-REGULATING FACTORs (GRFs) are plant-specific transcription factors that play important roles in regulating plant growth, development, and tolerance to stresses. However, there has been no in-depth research on the GRF genes and their roles in apple. A total of sixteen GRF genes were identified in the apple genome (GDDH13 V1.1), that expressed differentially in various tissues, in which the highest expression levels were observed particularly in shoot tips and apical buds. Among MdGRFs, the MdGRF11 was cloned and further investigated. Overexpression of the MdGRF11 in Arabidopsis plants promoted flowering, root elongation and leaf size. Further investigation indicated that MdGRF11 interacts with key flower genes FLOWERING LOCUS T (FT) and TERMINAL FLOWER1 (TFL1). The transient assays demonstrated that MdGRF11 represses the expression of knotted-like homeobox (MdKNOX19). Furthermore, MdTFL1 can compete with MdFT1 for complex formation with MdGRF11 to regulate the expression of MdKNOX19. Taken together, our results suggest that MdGRF11 protein is involved in fine-tuning of the floral transition possibly through interaction with the MdFT1 and MdTFL1 proteins.

Overexpression of HANABA TARANU in cultivated strawberry delays flowering and leads to defective flower and fruit development

Cultivated strawberry is one of the most important horticultural crops in the world, and the fruit yields and economic benefits are largely dependent on the quality of floral initiation and floral organ development. However, the underlying regulatory mechanisms controlling these processes in strawberry are largely unknown. In this study, the function of a GATA transcription factor gene, HANABA TARANU (HAN), in floral initiation and floral organ development was characterized in strawberry. FaHAN is expressed in four whorls of the floral organs. Overexpression (OE) of FaHAN in the strawberry cultivar ‘Benihoppe’ delayed flowering by at least one week by affecting key genes, such as TERMINAL FLOWER 1, APETALA 1…and increased the number of runners. FaHAN-OE plants also showed malformed floral organs, especially the deformed stigmas with disordered arrangement. Several key genes for pistil apical development such as STYLISH, YUCCA 1, and auxin-related genes such as GH3.5, PIN-FORMED 1, which play important roles in pistil primordium development in many plant species, were all down-regulated in FaHAN-OE plants. Further observations showed that the fruit deformity rate was nearly 4-fold higher than in control plants. Together, this study provides a new approach for exploring floral initiation and floral organ development in strawberry.

Isolation and Functional Characterization of a LEAFY Gene in Mango (Mangifera indica L.).

LEAFY (LFY) plays an important role in the flowering process of plants, controlling flowering time and mediating floral meristem differentiation. Owing to its considerable importance, the mango LFY gene (MiLFY; GenBank accession no. HQ585988) was isolated, and its expression pattern and function were characterized in the present study. The cDNA sequence of MiLFY was 1152 bp, and it encoded a 383 amino acid protein. MiLFY was expressed in all tested tissues and was highly expressed in flowers and buds. Temporal expression analysis showed that MiLFY expression was correlated with floral development stage, and two relative expression peaks were detected in the early stages of floral transition and floral organ differentiation. Moreover, 35S::GFP-MiLFY fusion protein was shown to be localized to the nucleus of cells. Overexpression of MiLFY in Arabidopsis promoted early flowering and the conversion of lateral meristems into terminal flowers. In addition, transgenic plants exhibited obvious morphological changes, such as differences in cauline leaf shape, and the number of lateral branches. When driven by the MiLFY promoter, GFP was highly expressed in leaves, floral organs, stems, and roots, during the flowering period. Exogenous gibberellin (GA3) treatment downregulated MiLFY promoter expression, but paclobutrazol (PPP333) upregulated it. Bimolecular fluorescence complementation (BiFC) assays showed that the MiLFY protein can interact with zinc-finger protein 4 (ZFP4) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (MiSOC1D). Taken together, these results indicate that MiLFY plays a pivotal role in controlling mango flowering, and that it is regulated by gibberellin and paclobutrazol.

Identification of a major locus for flowering pattern sheds light on plant architecture diversification in cultivated peanut.

A major gene controls flowering pattern in peanut, possibly encoding a TFL1-like. It was subjected to gain/loss events of a deletion and changes in mRNA expression levels, partly explaining the evolution of flowering pattern in Arachis. Flowering pattern (FP) is a major characteristic differentiating the two subspecies of cultivated peanut (Arachis hypogaea L.). Subsp. fastigiata possessing flowers on the mainstem (MSF) and a sequential FP, whereas subsp. hypogaealacks MSF and exhibits an alternate FP. FP is considered the main contributor to plant adaptability, and evidence indicates that its diversification occurred during the several thousand years of domestication. However, the genetic mechanism that controls FP in peanut is unknown. We investigated the genetics of FP in a recombinant inbred population, derivatives of an A. hypogaea by A. fastigiata cross. Lines segregated 1:1 for FP, indicating a single gene effect. Using Axiom_Arachis2 SNP-array, FP was mapped to a small segment in chromosome B02, wherein a Terminal Flowering 1-like (AhTFL1) gene with a 1492bp deletion was found in the fastigiata line, leading to a truncated protein. Remapping FP in the RIL population with the AhTFL1 indel as a marker increased the LOD score from 53.3 to 158.8 with no recombination in the RIL population. The same indel was found co-segregating with the phenotype in two independent EMS-mutagenized M2 families, suggesting a hotspot for gene conversion. Also, AhTFL1 was significantly less expressed in the fastigiata line compared to hypogaea and in flowering than non-flowering branches. Sequence analysis of the AhTFL1 in peanut world collections indicated significant conservation, supporting the putative role of AhTFL1 in peanut speciation during domestication and modern cultivation.

SEPALLATA--like genes of Isatis indigotica can affect the architecture of the inflorescences and the development of the floral organs.

BackgroundThe architecture of inflorescence and the development of floral organs can influence the yield of seeds and have a significant impact on plant propagation. E-class floral homeotic MADS-box genes exhibit important roles in regulation of floral transition and differentiation of floral organs. Woad (Isatis indigotica) possesses unique inflorescence, floral organs and fruit. However, very little research has been carried out to determine the function of MADS-box genes in this medicinal cruciferous plant species.ResultsSEPALLATA orthologs in I. indigotica were cloned by degenerate PCR. The sequence possessing the highest identity with SEP2 and SEP4 of Arabidopsis were named as IiSEP2 and IiSEP4, respectively. Constitutive expression of IiSEP2 in Columbia (Col-0) ecotype of Arabidopsis led to early flowering, and the number of the flowers and the lateral branches was reduced, indicating an alteration in architecture of the inflorescences. Moreover, the number of the floral organs was declined, the sepals were turned into carpelloid tissues bearing stigmatic papillae and ovules, and secondary flower could be produced in apetalous terminal flowers. In 35S::IiSEP4-GFP transgenic Arabidopsis plants in Landsberg erecta (Ler) genetic background, the number of the floral organs was decreased, sepals were converted into curly carpelloid structures, accompanied by generation of ovules. Simultaneously, the size of petals, stamens and siliques was diminished. In 35S::IiSEP4-GFP transgenic plants of apetalous ap1 cal double mutant in Ler genetic background, the cauliflower phenotype was attenuated significantly, and the petal formation could be rescued. Occasionally, chimeric organs composed of petaloid and sepaloid tissues, or petaloid and stamineous tissues, were produced in IiSEP4 transgenic plants of apl cal double mutant. It suggested that overexpression of IiSEP4 could restore the capacity in petal differentiation. Silencing of IiSEP4 by Virus-Induced Gene Silencing (VIGS) can delay the flowering time, and reduce the number and size of the floral organs in woad flowers.ConclusionAll the results showed that SEPALLATA-like genes could influence the architecture of the inflorescence and the determinacy of the floral meristems, and was also related to development of the floral organs.

Natural Variation in the Control of Flowering and Shoot Architecture in Diploid Fragaria Species.

In perennial fruit and berry crops of the Rosaceae family, flower initiation occurs in late summer or autumn after downregulation of a strong repressor TERMINAL FLOWER1 (TFL1), and flowering and fruiting takes place the following growing season. Rosaceous fruit trees typically form two types of axillary shoots, short flower-bearing shoots called spurs and long shoots that are, respectively, analogous to branch crowns and stolons in strawberry. However, regulation of flowering and shoot architecture differs between species, and environmental and endogenous controlling mechanisms have just started to emerge. In woodland strawberry (Fragaria vesca L.), long days maintain vegetative meristems and promote stolon formation by activating TFL1 and GIBBERELLIN 20-OXIDASE4 (GA20ox4), respectively, while silencing of these factors by short days and cool temperatures induces flowering and branch crown formation. We characterized flowering responses of 14 accessions of seven diploid Fragaria species native to diverse habitats in the northern hemisphere and selected two species with contrasting environmental responses, Fragaria bucharica Losinsk. and Fragaria nilgerrensis Schlecht. ex J. Gay for detailed studies together with Fragaria vesca. Similar to F. vesca, short days at 18°C promoted flowering in F. bucharica, and the species was induced to flower regardless of photoperiod at 11°C after silencing of TFL1. F. nilgerrensis maintained higher TFL1 expression level and likely required cooler temperatures or longer exposure to inductive treatments to flower. We also found that high expression of GA20ox4 was associated with stolon formation in all three species, and its downregulation by short days and cool temperature coincided with branch crown formation in F. vesca and F. nilgerrensis, although the latter did not flower. F. bucharica, in contrast, rarely formed branch crowns, regardless of flowering or GA20ox4 expression level. Our findings highlighted diploid Fragaria species as rich sources of genetic variation controlling flowering and plant architecture, with potential applications in breeding of Rosaceous crops.

Flower and Spikelet Construction in Rapateaceae (Poales).

The family Rapateaceae represents an early-divergent lineage of Poales with biotically pollinated showy flowers. We investigate developmental morphology and anatomy in all three subfamilies and five tribes of Rapateaceae to distinguish between contrasting hypotheses on spikelet morphology and to address questions on the presence of nectaries and gynoecium structure. We support an interpretation of the partial inflorescence (commonly termed spikelet), as a uniaxial system composed of a terminal flower and numerous empty phyllomes. A terminal flower in an inflorescence unit is an autapomorphic feature of Rapateaceae. The gynoecium consists of synascidiate, symplicate, and usually asymplicate zones, with gynoecium formation encompassing congenital and often also postgenital fusions between carpels. Species of Rapateaceae differ in the relative lengths of the gynoecial zones, the presence or absence of postgenital fusion between the carpels and placentation in the ascidiate or plicate carpel zones. In contrast with previous reports, septal nectaries are lacking in all species. The bird-pollinated tribe Schoenocephalieae is characterized by congenital syncarpy; it displays an unusual type of gynoecial (non-septal) nectary represented by a secretory epidermis at the gynoecium base.

Untangling inflorescences in Miconieae (Melastomataceae): development, typology, and the systematic and evolutionary implications.

This study aimed to describe the origin, position, development and typology of inflorescences in Miconieae through ontogenetic and morphological analyses using light microscopy. We observed three morphological character states: terminal, pseudo-axillary and axillary; and two ontogenetic states: terminal and axillary. The terminal and pseudoaxillary inflorescences originate from terminal reproductive meristems. Pseudoaxillary inflorescences result from unequal development of vegetative meristems which flank the terminal flowering unit, whereas in terminal inflorescences, both vegetative meristems develop equally. In axillary inflorescences, the terminal reproductive meristem is not involved, while axillary inflorescences originate from reproductive axillary meristems. The inflorescences range from heterocladic and thyrsoid to simpler types, such as botryoid and triad. Such characteristics can also be seen in paracladia, particularly those most distal. The terminal inflorescence is observed in all clades of Miconieae, and pseudoaxillary and axillary inflorescences should be apomorphic states in the tribe and derived from the terminal condition.

Analysis of the PEBP gene family and identification of a novel FLOWERING LOCUS T orthologue in sugarcane.

Sugarcane (Saccharum spp.) is an important economic crop for both sugar and biomass, the yields of which are negatively affected by flowering. The molecular mechanisms controlling flowering in sugarcane are nevertheless poorly understood. RNA-seq data analysis and database searches have enabled a comprehensive description of the PEBP gene family in sugarcane. It is shown to consist of at least 13 FLOWERING LOCUS T (FT)-like genes, two MOTHER OF FT AND TFL (MFT)-like genes, and four TERMINAL FLOWER (TFL)-like genes. As expected, these genes all show very high homology to their corresponding genes in Sorghum, and also to FT-like, MFT-like, and TFL-like genes in maize, rice, and Arabidopsis. Functional analysis in Arabidopsis showed that the sugarcane ScFT3 gene can rescue the late flowering phenotype of the Arabidopsis ft-10 mutant, whereas ScFT5 cannot. High expression levels of ScFT3 in leaves of short day-induced sugarcane plants coincided with initial stages of floral induction in the shoot apical meristem as shown by histological analysis of meristem dissections. This suggests that ScFT3 is likely to play a role in floral induction in sugarcane; however, other sugarcane FT-like genes may also be involved in the flowering process.

Role of gibberellin and its three GID1 receptors in Jasminum sambac stem elongation and flowering.

Taken together, our results establish a reciprocalrelationship between vine elongationandflowering, and reveal that GA is a positive signal for stem elogation but a negative regulator of flowering in this species. Vines or climbing plants exhibit vigorous vegetative shoot extension. GA have long been recognized as an important signal for seasonal stem elongation and flowering in many woody perennials. However, less is explored as how GA pathway is involved in the regulation of shoot extension in woody vines. Here, we investigated the role of GA and its signaling components in shoot elongation in Jasminum sambac. We found high accumulation of GA4 in the elongating internode, in contrast to a depletion of GAs in the floral differentiating shoot, which in turn featured a higher zeatin content, and a lower IAA and JA concentrations. This GA accumulation was coincident with the strong expression of JsGA20ox1 and JsGAS1 in the leaves, as well as of the JsGA2ox3 in the internode. Treatment of GA biosynthesis inhibitor reduced elongation while stimulated the terminal flowering. Remarkably, three B-type GA-receptor genes were abundantly expressed in both internodes and leaves of the extending shoots, which could enhance GA responsiveness in heterologous transgenic Arabidopsis. Furthermore, these JsGID1s showed distinct GA-dependent interaction with the JsDELLA in a yeast-two-hybrid assay. Taken together, our results establish a reciprocal relationship between vine elongation and flowering, and reveal that GA is a positive signal for stem elogation but a negative regulator of flowering in this species.

A novel TFL1 gene induces flowering in the mast seeding alpine snow tussock, Chionochloa pallens (Poaceae).

Masting, the synchronous, highly variable flowering across years by a population of perennial plants, has been reported to be precipitated by various factors including nitrogen levels, drought conditions, and spring and summer temperatures. However, the molecular mechanism leading to the initiation of flowering in masting plants in particular years remains largely unknown, despite the potential impact of climate change on masting phenology. We studied genes controlling flowering in the alpine snow tussock Chionochloa pallens (Poaceae), a strongly masting perennial grass. We used a range of in situ and manipulated plants to obtain leaf samples from tillers (shoots) which subsequently remained vegetative or flowered. Here, we show that a novel orthologue of TERMINAL FLOWER 1 (TFL1; normally a repressor of flowering in other species) promotes the induction of flowering in C. pallens (hence Anti-TFL1), a conclusion supported by structural, functional and expression analyses. Global transcriptomic analysis indicated differential expression of CpTPS1, CpGA20ox1, CpREF6 and CpHDA6, emphasizing the role of endogenous cues and epigenetic regulation in terms of responsiveness of plants to initiate flowering. Our molecular-based study provides insights into the cellular mechanism of flowering in masting plants and will supplement ecological and statistical models to predict how masting will respond to global climate change.

Bambusa nghiana sp. nov. (Poaceae: Bambusoideae), a new species from Thanh Hoa Province, Vietnam

A new species of Bambusa (Poaceae: Bambusoideae), B. nghiana V.T. Tran, sp. nov., is described and illustrated from Thanh Hoa Province, Vietnam. This species is similar to B. gurgandii K.M.Wong & Diep, but differs by its long internodes, blade auricles lobed and not spreading, and upcurved at the end, 2-4 perfect flowers, one terminal vestigial flower.

The branchless gene Clbl in watermelon encoding a TERMINAL FLOWER 1 protein regulates the number of lateral branches

The branchless gene Clbl in watermelon encoding a TERMINAL FLOWER 1 protein regulates the number of lateral branches

Asymmetric expansions of FT and TFL1 lineages characterize differential evolution of the EuPEBP family in the major angiosperm lineages

BackgroundIn flowering plants, precise timing of the floral transition is crucial to maximize chances of reproductive success, and as such, this process has been intensively studied. FLOWERING LOCUS T (FT) and TERMINAL FLOWER1 (TFL1) have been identified as closely related eukaryotic phosphatidylethanolamine-binding proteins (‘EuPEBPs’) that integrate multiple environmental stimuli, and act antagonistically to determine the optimal timing of the floral transition. Extensive research has demonstrated that FT acts similar to hormonal signals, being transported in the phloem from its primary site of expression in leaves to its primary site of action in the shoot meristem; TFL1 also appears to act as a mobile signal. Recent work implicates FT, TFL1, and the other members of the EuPEBP family, in the control of other important processes, suggesting that the EuPEBP family may be key general regulators of developmental transitions in flowering plants. In eudicots, there are a small number of EuPEBP proteins, but in monocots, and particularly grasses, there has been a large, but uncharacterized expansion of EuPEBP copy number, with unknown consequences for the EuPEBP function.ResultsTo systematically characterize the evolution of EuPEBP proteins in flowering plants, and in land plants more generally, we performed a high-resolution phylogenetic analysis of 701 PEBP sequences from 208 species. We refine previous models of EuPEBP evolution in early land plants, demonstrating the algal origin of the family, and pin-pointing the origin of the FT/TFL1 clade at the base of monilophytes. We demonstrate how a core set of genes (MFT1, MFT2, FT, and TCB) at the base of flowering plants has undergone differential evolution in the major angiosperm lineages. This includes the radical expansion of the FT family in monocots into 5 core lineages, further re-duplicated in the grass family to 12 conserved clades.ConclusionsWe show that many grass FT proteins are strongly divergent from other FTs and are likely neo-functional regulators of development. Our analysis shows that monocots and eudicots have strongly divergent patterns of EuPEBP evolution.

Identification of apple TFL1-interacting proteins uncovers an expanded flowering network

MdTFL1, a floral repressor, forms protein complexes with several proteins and could compete with MdFT1 to regulate reproductive development in apple. Floral transition is a key developmental stage in the annual growth cycle of perennial fruit trees that directly determines the fruit development in the subsequent stage. FLOWERING LOCUS T (FT)/TERMINAL FLOWER1 (TFL1) family is known to play a vital regulatory role in plant growth and flowering. In apple, the two TFL1-like genes (MdTFL1-1 and MdTFL1-2) function as floral inhibitors; however, their mechanism of action is still largely unclear. This study aimed to functionally validate MdTFL1 and probe into its mechanism of action in apple. MdTFL1-1 and MdTFL1-2 were expressed mainly in stem and apical buds of vegetative shoots, with little expression in flower buds and young fruit. Expression of MdTFL1-1 and MdTFL1-2 rapidly decreased during floral induction. On the other hand, transgenic Arabidopsis, which ectopically expressed MdTFL1-1 or MdTFL1-2, flowered later than wild-type plants; demonstrating their in planta capability to function redundantly as flower repressors. Furthermore, we identified hundreds of novel interaction proteins of the two apple MdTFL1 proteins using yeast two-hybrid screens. Independent experiments for several proteins confirmed the yeast two-hybrid interactions. Among them, the transcription factor Nuclear Factor-Y subunit C (MdNF-YC2) functions as a promoter of flowering in Arabidopsis by activating LEAFY (LFY) and APETALA1 (AP1) expression. MdFT1 showed a similar interaction pattern as MdTFL1, implying a possible antagonistic action in the regulation of flowering. These newly identified TFL1-interacting proteins (TIPs) not only expand the floral regulatory network, but may also introduce new roles for TFL1 in plant development.

Morphological, Physiological, and Molecular Responses of Sweetly Fragrant Luculia gratissima During the Floral Transition Stage Induced by Short-Day Photoperiod.

Photoperiod-regulated floral transition is vital to the flowering plant. Luculia gratissima “Xiangfei” is a flowering ornamental plant with high development potential economically and is a short-day woody perennial. However, the genetic regulation of short-day-induced floral transition in L. gratissima is unclear. To systematically research the responses of L. gratissima during this process, dynamic changes in morphology, physiology, and transcript levels were observed and identified in different developmental stages of long-day- and short-day-treated L. gratissima plants. We found that floral transition in L. gratissima occurred 10 d after short-day induction, but flower bud differentiation did not occur at any stage under long-day conditions. A total of 1,226 differentially expressed genes were identified, of which 146 genes were associated with flowering pathways of sugar, phytohormones, photoperiod, ambient temperature, and aging signals, as well as floral integrator and meristem identity genes. The trehalose-6-phosphate signal positively modulated floral transition by interacting with SQUAMOSA PROMOTER-BINDING-LIKE PROTEIN 4 (SPL4) in the aging pathway. Endogenous gibberellin, abscisic acid, cytokinin, and jasmonic acid promoted floral transition, whereas strigolactone inhibited it. In the photoperiod pathway, FD, CONSTANS-LIKE 12, and nuclear factors Y positively controlled floral transition, whereas PSEUDO-RESPONSE REGULATOR 7, FLAVIN-BINDING KELCH REPEAT F-BOX PROTEIN 1, and LUX negatively regulated it. SPL4 and pEARLI1 positively affected floral transition. Suppressor of Overexpression of Constans 1 and AGAMOUSLIKE24 integrated multiple flowering signals to modulate the expression of FRUITFULL/AGL8, AP1, LEAFY, SEPALLATAs, SHORT VEGETATIVE PHASE, and TERMINAL FLOWER 1, thereby regulating floral transition. Finally, we propose a regulatory network model for short-day-induced floral transition in L. gratissima. This study improves our understanding of flowering time regulation in L. gratissima and provides knowledge for its production and commercialization.

The FveFT2 florigen/FveTFL1 antiflorigen balance is critical for the control of seasonal flowering in strawberry while FveFT3 modulates axillary meristem fate and yield.

Summary Plant architecture is central in determining crop yield. In the short‐day species strawberry, a crop vegetatively propagated by daughter‐plants produced by stolons, fruit yield is further dependent on the trade‐off between sexual reproduction (fruits) and asexual reproduction (daughter‐plants). Both are largely dependent on meristem identity, which establishes the development of branches, stolons and inflorescences.Floral initiation and plant architecture are modulated by the balance between two related proteins, FLOWERING LOCUS T (FT) and TERMINAL FLOWER 1 (TFL1). We explored in woodland strawberry the role of the uncharacterised FveFT2 and FveFT3 genes and of the floral repressor FveTFL1 through gene expression analyses, grafting and genetic transformation (overexpression and gene editing).We demonstrate the unusual properties of these genes. FveFT2 is a nonphotoperiodic florigen permitting short‐day (SD) flowering and FveTFL1 is the long‐hypothesised long‐day systemic antiflorigen that contributes, together with FveFT2, to the photoperiodic regulation of flowering. We additionally show that FveFT3 is not a florigen but promotes plant branching when overexpressed, that is likely to be through changing axillary meristem fate, therefore resulting in a 3.5‐fold increase in fruit yield at the expense of stolons.We show that our findings can be translated into improvement of cultivated strawberry in which FveFT2 overexpression significantly accelerates flowering.

LEAFY, a Pioneer Transcription Factor in Plants: A Mini-Review.

A subset of eukaryotic transcription factors (TFs) possess the ability to reprogram one cell type into another. Genes important for cellular reprograming are typically located in closed chromatin, which is covered by nucleosomes. Pioneer factors are a special class of TFs that can initially engage their target sites in closed chromatin prior to the engagement with, opening of, or modification of the sites by other factors. Although many pioneer factors are known in animals, a few have been characterized in plants. The TF LEAFY (LFY) acts as a pioneer factor specifying floral fate in Arabidopsis. In response to endogenous and environmental cues, plants produce appropriate floral inducers (florigens). During the vegetative phase, LFY is repressed by the TERMINAL FLOWER 1 (TFL1)–FD complex, which functions as a floral inhibitor, or anti-florigen. The florigen FLOWERING LOCUS T (FT) competes with TFL1 to prevent the binding of the FD TF to the LFY locus. The resulting FT–FD complex functions as a transient stimulus to activate its targets. Once LFY has been transcribed in the appropriate spatiotemporal manner, LFY binds to nucleosomes in closed chromatin regions. Subsequently, LFY opens the chromatin by displacing H1 linker histones and recruiting the SWI/SNF chromatin-remodeling complex. Such local changes permit the binding of other TFs, leading to the expression of the floral meristem identity gene APETALA1. This mini-review describes the latest advances in our understanding of the pioneer TF LFY, providing insight into the establishment of gene expression competence through the shaping of the plant epigenetic landscape.

Ectopic expression of the Arabidopsis florigen gene FLOWERING LOCUS T in seeds enhances seed dormancy via the GA and DOG1 pathways.

Ectopic expression of specific genes in seeds could be a tool for molecular design of crops to alter seed dormancy and germination, thereby improving production. Here, a seed-specific vector, 12S-pLEELA, was applied to study the roles of genes in Arabidopsis seeds. Transgenic lines containing FLOWERING LOCUS T (FT) driven by the 12S promoter exhibited significantly increased seed dormancy and earlier flowering. Mutated FT(Y85H) and TERMINAL FLOWER1 (TFL1) transgenic lines also showed increased seed dormancy but without altered flowering time. FT(Y85H) and TFL1 caused weaker seed dormancy enhancement compared to FT. The FT and TFL1 transgenic lines showed hypersensitivity to paclobutrazol, but not to abscisic acid in seed germination. The levels of bioactive gibberellin 3 (GA3 ) and GA4 were significantly reduced, consistent with decreased expression of COPALYL DIPHOSPHATE SYNTHASE (CPS), KAURENE OXIDASE (KO), GIBBERELLIN 3-OXIDASE2 (GA3ox2), and GA20ox1 in p12S::FT lines. Exogenous GA4+7 could recover the germination ability of FT transgenic lines. These results revealed that FT regulates GA biosynthesis. A genetic analysis indicated that the GA signaling regulator SPINDLY (SPY) is epistatic to FT in GA-mediated seed germination. Furthermore, DELAY OF GERMINATION1 (DOG1) showed significantly higher transcript levels in p12S::FT lines. Seed dormancy analysis of dog1-2 spy-3 p12S::FT-2 indicated that the combination of SPY and DOG1 is epistatic to FT in the regulation of dormancy. Overall, we showed that ectopic expression of FT and TFL1 in seeds enhances dormancy through affecting GA and DOG1 pathways.