Finding the right balance: The enduring role of florigens during cereal inflorescence development and their influence on fertility.

Flowering is a vital process in a plant's lifecycle and variation for flowering-time has helped cereals adapt to diverse environments. Much cereal research has focused on understanding how flowering signals, or florigens, regulate the floral transition and timing of ear emergence. However, flowering genes also perform an enduring role during inflorescence development, with genotypes that elicit a weaker flowering signal producing more elaborately branched inflorescences with extra floret-bearing spikelets. While this outcome indicates that variable expression of flowering genes could boost yield potential, further analysis has shown that dampened florigen levels can compromise fertility, negating the benefit of extra grain-producing sites. Here, we discuss ways that florigens contribute to early and late inflorescence development, including their influence on branch/spikelet architecture and fertility. We propose that a deeper understanding of the role for florigens during inflorescence development could be used to balance the effects of florigens throughout flowering to improve productivity.

RuBisCO Depletion and Subcellular Fractionation for Enhanced Florigen Detection in Arabidopsis.

In plants, complex signaling networks monitor and respond to environmental cues to determine the optimal time for the transition from the vegetative to reproductive phase. Understanding these networks requires robust tools to examine the levels and subcellular localization of key factors. The florigen FLOWERING LOCUS T (FT) is a crucial regulator of flowering time and occurs in soluble and membrane-bound forms. At low ambient temperatures, the ratio of these forms of FT undergoes a significant shift, which leads to a delay in the onset of flowering. To investigate these changes in FT localization, epitope-tagged FT protein can be isolated from plants by subcellular fractionation and its localization examined by immunoblot analysis of the resulting fractions. However, the highly abundant protein ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) can interfere with methods to detect and characterize low-abundance proteins such as FT. In this chapter, we present a method for analyzing the ratio of HA-tagged FT (HA:FT) in different subcellular fractions while mitigating the interference from RuBisCO by using protamine sulfate (PS) to deplete RuBisCO during protein purification, thereby enhancing HA:FT detection in fractionated samples.

Sorghum SbGhd7 is a major regulator of floral transition and directly represses genes crucial for flowering activation.

Molecular genetic understanding of flowering time regulation is crucial for sorghum development. GRAIN NUMBER, PLANT HEIGHT AND HEADING DATE 7 (SbGhd7) is one of the six classical loci conferring photoperiod sensitivity of sorghum flowering. However, its functions remain poorly studied. The molecular functions of SbGhd7 were characterized. The gene regulatory network controlled by SbGhd7 was constructed and validated. The biological roles of SbGhd7 and its major targets were studied. SbGhd7 overexpression (OE) completely prevented sorghum flowering. Additionally, we show that SbGhd7 is a major negative regulator of flowering, binding to the promoter motif TGAATG(A/T)(A/T/C) and repressing transcription of the major florigen FLOWERING LOCUS T 10 (SbFT10) and floral activators EARLY HEADING DATE (SbEhd1), FLAVIN-BINDING, KELCH REPEAT, F-BOX1 (SbFKF1) and EARLY FLOWERING 3 (SbELF3). Reinforcing the direct effect of SbGhd7, SbEhd1 OE activated the promoters of three functional florigens (SbFT1, SbFT8 and SbFT10), dramatically accelerating flowering. Our studies demonstrate that SbGhd7 is a major repressor of sorghum flowering by directly and indirectly targeting genes for flowering activation. The mechanism appears ancient. Our study extends the current model of floral transition regulation in sorghum and provides a framework for a comprehensive understanding of sorghum photoperiod response.

The Function of Florigen in the Vegetative-to-Reproductive Phase Transition in and around the Shoot Apical Meristem.

Plants undergo a series of developmental phases throughout their life-cycle, each characterized by specific processes. Three critical features distinguish these phases: the arrangement of primordia (phyllotaxis), the timing of their differentiation (plastochron) and the characteristics of the lateral organs and axillary meristems. Identifying the unique molecular features of each phase, determining the molecular triggers that cause transitions and understanding the molecular mechanisms underlying these transitions are keys to gleaning a complete understanding of plant development. During the vegetative phase, the shoot apical meristem (SAM) facilitates continuous leaf and stem formation, with leaf development as the hallmark. The transition to the reproductive phase induces significant changes in these processes, driven mainly by the protein FT (FLOWERING LOCUS T) in Arabidopsis and proteins encoded by FT orthologs, which are specified as 'florigen'. These proteins are synthesized in leaves and transported to the SAM, and act as the primary flowering signal, although its impact varies among species. Within the SAM, florigen integrates with other signals, culminating in developmental changes. This review explores the central question of how florigen induces developmental phase transition in the SAM. Future research may combine phase transition studies, potentially revealing the florigen-induced developmental phase transition in the SAM.

Rice florigens control a common set of genes at the shoot apical meristem including the F-BOX BROADER TILLER ANGLE 1 that regulates tiller angle and spikelet development.

Rice flowering is triggered by transcriptional reprogramming at the shoot apical meristem (SAM) mediated by florigenic proteins produced in leaves in response to changes in photoperiod. Florigens are more rapidly expressed under short days (SDs) compared to long days (LDs) and include the HEADING DATE 3a (Hd3a) and RICE FLOWERING LOCUS T1 (RFT1) phosphatidylethanolamine binding proteins. Hd3a and RFT1 are largely redundant at converting the SAM into an inflorescence, but whether they activate the same target genes and convey all photoperiodic information that modifies gene expression at the SAM is currently unclear. We uncoupled the contribution of Hd3a and RFT1 to transcriptome reprogramming at the SAM by RNA sequencing of dexamethasone-inducible over-expressors of single florigens and wild-type plants exposed to photoperiodic induction. Fifteen highly differentially expressed genes common to Hd3a, RFT1, and SDs were retrieved, 10 of which still uncharacterized. Detailed functional studies on some candidates revealed a role for LOC_Os04g13150 in determining tiller angle and spikelet development and the gene was renamed BROADER TILLER ANGLE 1 (BRT1). We identified a core set of genes controlled by florigen-mediated photoperiodic induction and defined the function of a novel florigen target controlling tiller angle and spikelet development.

Adaptation to high latitudes through a novel allele of Hd3a strongly promoting heading date in rice.

KEY MESSAGE: A novel Hd3a allele strongly promoting rice heading date was identified, and it functions through florigen activation complex (FAC) and was selected during the spread of rice cultivation to high-latitude areas. Heading date is a critical agronomic trait for rice that determines the utilization of light and temperature conditions and thereby affects grain yield. Rice is a short day (SD) plant, and its photoperiodic information is processed by complex pathways and integrated by florigens to control flowering. In this study, we identified a novel allele for the florigen gene Heading date 3a (Hd3a), characterized by a C435G substitution in its coding region, by a genome-wide association study (GWAS) approach in a panel of 199 high-latitude japonica rice varieties. The C435G substitution induces plants to flower 10 days earlier in high-latitude area (long day condition). Then, we mutated C435 to G in Hd3a by prime editing and found the point mutation plants flowered 12 days earlier. Further molecular experiments showed the novel Hd3a protein can interact with GF14b protein and increase the expression of OsMADS14, the output gene of florigen activation complex (FAC). Molecular signatures of selection indicated that the novel Hd3a allele was selected during the process of rice cultivation expansion into high-latitude areas. Collectively, these results provide new insights into heading date regulation in high-latitude areas and advance improvements to rice adaptability to enhance crop yield.

The bZIP transcription factor AREB3 mediates FT signalling and floral transition at the Arabidopsis shoot apical meristem.

The floral transition occurs at the shoot apical meristem (SAM) in response to favourable external and internal signals. Among these signals, variations in daylength (photoperiod) act as robust seasonal cues to activate flowering. In Arabidopsis, long-day photoperiods stimulate production in the leaf vasculature of a systemic florigenic signal that is translocated to the SAM. According to the current model, FLOWERING LOCUS T (FT), the main Arabidopsis florigen, causes transcriptional reprogramming at the SAM, so that lateral primordia eventually acquire floral identity. FT functions as a transcriptional coregulator with the bZIP transcription factor FD, which binds DNA at specific promoters. FD can also interact with TERMINAL FLOWER 1 (TFL1), a protein related to FT that acts as a floral repressor. Thus, the balance between FT-TFL1 at the SAM influences the expression levels of floral genes targeted by FD. Here, we show that the FD-related bZIP transcription factor AREB3, which was previously studied in the context of phytohormone abscisic acid signalling, is expressed at the SAM in a spatio-temporal pattern that strongly overlaps with FD and contributes to FT signalling. Mutant analyses demonstrate that AREB3 relays FT signals redundantly with FD, and the presence of a conserved carboxy-terminal SAP motif is required for downstream signalling. AREB3 shows unique and common patterns of expression with FD, and AREB3 expression levels are negatively regulated by FD thus forming a compensatory feedback loop. Mutations in another bZIP, FDP, further aggravate the late flowering phenotypes of fd areb3 mutants. Therefore, multiple florigen-interacting bZIP transcription factors have redundant functions in flowering at the SAM.

Two florigens and a florigen-like protein form a triple regulatory module at the shoot apical meristem to promote reproductive transitions in rice.

Many plant species monitor and respond to changes in day length (photoperiod) for aligning reproduction with a favourable season. Day length is measured in leaves and, when appropriate, leads to the production of floral stimuli called florigens that are transmitted to the shoot apical meristem to initiate inflorescence development1. Rice possesses two florigens encoded by HEADING DATE 3a (Hd3a) and RICE FLOWERING LOCUS T 1 (RFT1)2. Here we show that the arrival of Hd3a and RFT1 at the shoot apical meristem activates FLOWERING LOCUS T-LIKE 1 (FT-L1), encoding a florigen-like protein that shows features partially differentiating it from typical florigens. FT-L1 potentiates the effects of Hd3a and RFT1 during the conversion of the vegetative meristem into an inflorescence meristem and organizes panicle branching by imposing increasing determinacy to distal meristems. A module comprising Hd3a, RFT1 and FT-L1 thus enables the initiation and balanced progression of panicle development towards determinacy.

OsFTL12, a member of FT-like family, modulates the heading date and plant architecture by florigen repression complex in rice.

FLOWERING LOCUS T (FT), a florigen in Arabidopsis, plays critical roles in floral transition. Among 13 FT-like members in rice, OsFTL2 (Hd3a) and OsFTL3 (RFT1), two rice homologues of FT, have been well characterized to act as florigens to induce flowering under short-day (SD) and long-day (LD) conditions, respectively, but the functions of other rice FT-like members remain largely unclear. Here, we show that OsFTL12 plays an antagonistic function against Hd3a and RFT1 to modulate the heading date and plant architecture in rice. Unlike Hd3a and RFT1, OsFTL12 is not regulated by daylength and highly expressed in both SD and LD conditions, and delays the heading date under either SD or LD conditions. We further demonstrate that OsFTL12 interacts with GF14b and OsFD1, two key components of the florigen activation complex (FAC), to form the florigen repression complex (FRC) by competing with Hd3a for binding GF14b. Notably, OsFTL12-FRC can bind to the promoters of the floral identity genes OsMADS14 and OsMADS15 and suppress their expression. The osmads14 osmads15 double mutants could not develop panicles and showed erect leaves. Taken together, our results reveal that different FT-like members can fine-tune heading date and plant architecture by regulating the balance of FAC and FRC in rice.

A bZIP transcription factor (CiFD) regulates drought- and low-temperature-induced flowering by alternative splicing in citrus.

Drought and low temperature are two key environmental factors that induce adult citrus flowering. However, the underlying regulation mechanism is poorly understood. The bZIP transcription factor FD is a key component of the florigen activation complex (FAC) which is composed of FLOWERING LOCUS T (FT), FD, and 14-3-3 proteins. In this study, isolation and characterization of CiFD in citrus found that there was alternative splicing (AS) of CiFD, forming two different proteins (CiFDα and CiFDß). Further investigation found that their expression patterns were similar in different tissues of citrus, but the subcellular localization and transcriptional activity were different. Overexpression of the CiFD DNA sequence (CiFD-DNA), CiFDα, or CiFDß in tobacco and citrus showed early flowering, and CiFD-DNA transgenic plants were the earliest, followed by CiFDß and CiFDα. Interestingly, CiFDα and CiFDß were induced by low temperature and drought, respectively. Further analysis showed that CiFDα can form a FAC complex with CiFT, Ci14-3-3, and then bind to the citrus APETALA1 (CiAP1) promoter and promote its expression. However, CiFDß can directly bind to the CiAP1 promoter independently of CiFT and Ci14-3-3. These results showed that CiFDß can form a more direct and simplified pathway that is independent of the FAC complex to regulate drought-induced flowering through AS. In addition, a bHLH transcription factor (CibHLH96) binds to CiFD promoter and promotes the expression of CiFD under drought condition. Transgenic analysis found that CibHLH96 can promote flowering in transgenic tobacco. These results suggest that CiFD is involved in drought- and low-temperature-induced citrus flowering through different regulatory patterns.

Homeobox transcription factors OsZHD1 and OsZHD2 induce inflorescence meristem activity at floral transition in rice.

Floral transition starts in the leaves when florigens respond to various environmental and developmental factors. Among several regulatory genes that are preferentially expressed in the inflorescence meristem during the floral transition, this study examines the homeobox genes OsZHD1 and OsZHD2 for their roles in regulating this transition. Although single mutations in these genes did not result in visible phenotype changes, double mutations in these genes delayed flowering. Florigen expression was not altered in the double mutants, indicating that the delay was due to a defect in florigen signaling. Morphological analysis of shoot apical meristem at the early developmental stage indicated that inflorescence meristem development was significantly delayed in the double mutants. Overexpression of ZHD2 causes early flowering because of downstream signals after the generation of florigens. Expression levels of the auxin biosynthesis genes were reduced in the mutants and the addition of indole-3-acetic acid recovered the defect in the mutants, suggesting that these homeobox genes play a role in auxin biosynthesis. A rice florigen, RICE FLOWERING LOCUS T 1, binds to the promoter regions of homeobox genes. These results indicate that florigens stimulate the expression of homeobox genes, enhancing inflorescence development in the shoot apex.

Multifunctional chemical inhibitors of the florigen activation complex discovered by structure-based high-throughput screening.

Structure-based high-throughput screening of chemical compounds that target protein-protein interactions (PPIs) is a promising technology for gaining insight into how plant development is regulated, leading to many potential agricultural applications. At present, there are no examples of using high-throughput screening to identify chemicals that target plant transcriptional complexes, some of which are responsible for regulating multiple physiological functions. Florigen, a protein encoded by FLOWERING LOCUS T (FT), was initially identified as a molecule that promotes flowering and has since been shown to regulate flowering and other developmental phenomena such as tuber formation in potato (Solanum tuberosum). FT functions as a component of the florigen activation complex (FAC) with a 14-3-3 scaffold protein and FD, a bZIP transcription factor that activates downstream gene expression. Although 14-3-3 is an important component of FAC, little is known about the function of the 14-3-3 protein itself. Here, we report the results of a high-throughput in vitro fluorescence resonance energy transfer (FRET) screening of chemical libraries that enabled us to identify small molecules capable of inhibiting FAC formation. These molecules abrogate the in vitro interaction between the 14-3-3 protein and the OsFD1 peptide, a rice (Oryza sativa) FD, by directly binding to the 14-3-3 protein. Treatment with S4, a specific hit molecule, strongly inhibited FAC activity and flowering in duckweed, tuber formation in potato, and branching in rice in a dose-dependent manner. Our results demonstrate that the high-throughput screening approach based on the three-dimensional structure of PPIs is suitable in plants. In this study, we have proposed good candidate compounds for future modification to obtain inhibitors of florigen-dependent processes through inhibition of FAC formation.

Expression of coffee florigen CaFT1 reveals a sustained floral induction window associated with asynchronous flowering in tropical perennials.

The behavior of florigen(s) and environment-influenced regulatory pathways that control floral initiation in tropical perennials species with complex phenological cycles is poorly understood. Understanding the mechanisms underlying this process is important for food production in the face of climate change, thus, we used Coffea sp. L. (Rubiaceae) as a model to explore this issue. Homologs of FLOWERING LOCUS T (CaFT1) and environment-related regulators CONSTANS (CaCO), PHYTOCHROME INTERACTING FACTOR 4 (CaPIF4) and FLOWERING LOCUS C (CaFLC) were retrieved from coffee genomes and identified through phylogenetic analysis. Overexpression of CaFT1 in Arabidopsis caused early-flowering phenotype and yeast two hybrid studies indicated CaFT1 binding to bZIP floral regulator FD, which suggests that CaFT1 is a coffee florigen. Expression of CaFT1 and other floral regulators, together with carbohydrate analysis, were evaluated over one year using three contrasting genotypes, two C. arabica cultivars and C. canephora. All genotypes showed active and variable CaFT1 transcription from February until October, indicating the potential window for floral induction that reached a maximum in the cold period of June. CaCO expression, as expected, varied over a 24-hour day period and monthly with day length, whereas expression of temperature-responsive homologs, CaFLC and CaPIF4, did not correlate with temperature changes nor CaFT1 expression, suggesting alternative FT regulatory pathways in coffee. Based on our results, we suggest a continuum of floral induction that allows different starting points for floral activation, which explains developmental asynchronicity and prolonged anthesis events in tropical perennial species.

From Floral Induction to Blooming: The Molecular Mysteries of Flowering in Woody Plants.

Flowering is a pivotal developmental process in response to the environment and determines the start of a new life cycle in plants. Woody plants usually possess a long juvenile nonflowering phase followed by an adult phase with repeated flowering cycles. The molecular mechanism underlying flowering regulation in woody plants is believed to be much more complex than that in annual herbs. In this review, we briefly describe the successive but distinct flowering processes in perennial trees, namely the vegetative phase change, the floral transition, floral organogenesis, and final blooming, and summarize in detail the most recent advances in understanding how woody plants regulate flowering through dynamic gene expression. Notably, the florigen gene FLOWERING LOCUS T(FT) and its antagonistic gene TERMINAL FLOWER 1 (TFL1) seem to play a central role in various flowering transition events. Flower development in different taxa requires interactions between floral homeotic genes together with AGL6 conferring floral organ identity. Finally, we illustrate the issues and corresponding measures of flowering regulation investigation. It is of great benefit to the future study of flowering in perennial trees.

Newly Discovered Alleles of the Tomato Antiflorigen Gene SELF PRUNING Provide a Range of Plant Compactness and Yield.

In tomato cultivation, a rare natural mutation in the flowering repressor antiflorigen gene SELF-PRUNING (sp-classic) induces precocious shoot termination and is the foundation in determinate tomato breeding for open field production. Heterozygous single flower truss (sft) mutants in the florigen SFT gene in the background of sp-classic provide a heterosis-like effect by delaying shoot termination, suggesting the subtle suppression of determinacy by genetic modification of the florigen-antiflorigen balance could improve yield. Here, we isolated three new sp alleles from the tomato germplasm that show modified determinate growth compared to sp-classic, including one allele that mimics the effect of sft heterozygosity. Two deletion alleles eliminated functional transcripts and showed similar shoot termination, determinate growth, and yields as sp-classic. In contrast, amino acid substitution allele sp-5732 showed semi-determinate growth with more leaves and sympodial shoots on all shoots. This translated to greater yield compared to the other stronger alleles by up to 42%. Transcriptome profiling of axillary (sympodial) shoot meristems (SYM) from sp-classic and wild type plants revealed six mis-regulated genes related to the floral transition, which were used as biomarkers to show that the maturation of SYMs in the weaker sp-5732 genotype is delayed compared to sp-classic, consistent with delayed shoot termination and semi-determinate growth. Assessing sp allele frequencies from over 500 accessions indicated that one of the strong sp alleles (sp-2798) arose in early breeding cultivars but was not selected. The newly discovered sp alleles are potentially valuable resources to quantitatively manipulate shoot growth and yield in determinate breeding programs, with sp-5732 providing an opportunity to develop semi-determinate field varieties with higher yields.

Quantitative Analysis of Florigen for the Variability of Floral Induction in Cabbage/Radish Inter-generic Grafting.

Grafting-induced flowering is a key phenomenon to understand systemic floral induction caused by florigen. It can also be used as a breeding technique enabling rapid seed production of crops with long generation times. However, the degree of floral induction in grafted plants is often variable. Moreover, it is difficult in some crop species. Here, we explored the factors promoting variability in the grafting-induced flowering of cabbage (Brassica oleracea L. var. capitata), an important vegetable crop with a long generation time, via the quantitative analysis of florigen accumulation. Significant variability in the flowering response of grafted cabbage was observed when rootstocks of different genotypes were used. As reported previously, B. oleracea rootstocks did not induce the flowering of grafted cabbage plants, but radish (Raphanus sativus L.) rootstocks unstably did, depending on the accessions used. Immunoblotting analysis of the FLOWERING LOCUS T (FT) protein, a main component of florigen, revealed that floral induction was quantitatively correlated with the level of accumulated FT protein in the grafted scion. To identify rootstock factors that cause variability in the floral induction of the grafted scion, we investigated FT protein accumulation and flowering response in grafted scions when the transcription levels of FT and the leaf area of rootstocks were altered by vernalization, daylength and leaf trimming treatments. We concluded that increasing the total amount of FT protein produced in the rootstock is important for the stable floral induction of the grafted cabbage, and this can be accomplished by increasing FT transcription and the leaf area of the rootstock.

Florigen repression complexes involving rice CENTRORADIALIS2 regulate grain size.

Grain size is one of the crucial factors determining grain yield. However, the genetic and molecular mechanisms of florigen repression complexes (FRCs) underlying grain size in rice (Oryza sativa L.) have not been reported. Here, we report that the rice CENTRORADIALIS (CEN) family member OsCEN2 (also known as Rice TFL1/CEN homolog, RCN1), a phosphatidylethanolamine-binding protein (PEBP) family protein, negatively controls grain size in rice. Overexpression of OsCEN2 led to small grains, and knockout of OsCEN2 resulted in large, heavy grains. OsCEN2 influenced grain size by restricting cell expansion in the spikelet hull and seed filling. In in vivo and in vitro experiments, OsCEN2 physically interacted with a G-box factor 14-3-3 homolog, GF14f, which negatively regulates grain size. Bimolecular fluorescence complementation and yeast two-hybrid assays revealed that GF14f directly interacts with the basic leucine zipper (bZIP) transcription factor, OsFD2. Plants overexpressing OsFD2 produced smaller and lighter grains than wild-type plants. We found that OsFD2 also influences grain size by controlling cell expansion and division in the spikelet hull. Our results reveal the molecular mechanisms of the OsCEN2-GF14f-OsFD2 regulatory module in controlling grain size. Additionally, our study provides insight into the functions of the FRC in rice and suggests a strategy for improving seed size and weight.

The tetratricopeptide repeat protein OsTPR075 promotes heading by regulating florigen transport in rice.

Rice (Oryza sativa) is one of the most important crops worldwide. Heading date is a vital agronomic trait that influences rice yield and adaption to local conditions. Hd3a, a proposed florigen that primarily functions under short-day (SD) conditions, is a mobile flowering signal that promotes the floral transition in rice. Nonetheless, how Hd3a is transported from leaves to the shoot apical meristem (SAM) under SDs remains elusive. Here, we report that FT-INTERACTING PROTEIN9 (OsFTIP9) specifically regulates rice flowering time under SDs by facilitating Hd3a transport from companion cells (CCs) to sieve elements (SEs). Furthermore, we show that the tetratricopeptide repeat (TPR) protein OsTPR075 interacts with both OsFTIP9 and OsFTIP1 and strengthens their respective interactions with Hd3a and the florigen RICE FLOWERING LOCUS T1 (RFT1). This in turn affects the trafficking of Hd3a and RFT1 to the SAM, thus regulating flowering time under SDs and long-day conditions, respectively. Our findings suggest that florigen transport in rice is mediated by different OsFTIPs under different photoperiods and those interactions between OsTPR075 and OsFTIPs are essential for mediating florigen movement from leaves to the SAM.

A comprehensive analysis of the floral transition in ma bamboo (Dendrocalamus latiflorus) reveals the roles of DlFTs involved in flowering.

Bamboo has a unique flowering characteristics of long and unpredictable vegetative period, which differs from annual herbs and perennial woody plants. In order to understand the molecular regulatory mechanism of bamboo flowering, a comprehensive study was conducted in ma bamboo (Dendrocalamus latiflorus Munro), including morphological, physiological and transcriptiome analyses. Differentially expressed genes related to the flowering pathway were identified by comparative transcriptome analysis. DlFT1, a homologous gene of FT/Hd3a, was significantly upregulated in flowering bamboo. Direct differentiation of spikelets from calli occurred and the downstream gene AP1 was upregulated in the transgenic bamboo overexpressing DlFT1. Transgenic rice overexpressing DlFT1 showed a strong early flowering phenotype. DlFT1 and DlTFL1 could interact with DlFD, and DlTFL1 delayed flowering. It is presumed that DlTFL1 plays an antagonistic role with DlFT1 in ma bamboo. In addition, the expression of DlFT1 was regulated by DlCO1, indicating that a CO-FT regulatory module might exist in ma bamboo. These results suggest that DlFT1 is a florigen candidate gene with conservative function in promoting flowering. Interestingly, the results have shown for the first time that DlFT2 can specifically interact with E3 ubiquitin ligase WAV3, while DlFT3 transcripts are mainly nonsense splicing. These findings provide better understanding of the roles of the florigen gene in bamboo and lay a theoretical basis for regulating bamboo flowering in the future.

The genetic architecture of flowering time changes in pea from wild to crop.

Change in phenology has been an important component in crop evolution, and selection for earlier flowering through a reduction in environmental sensitivity has helped broaden adaptation in many species. Natural variation for flowering in domesticated pea (Pisum sativum L.) has been noted and studied for decades, but there has been no clear account of change relative to its wild progenitor. Here we examined the genetic control of differences in flowering time between wild P. sativum ssp. humile and a typical late-flowering photoperiodic P. s. sativum accession in a recombinant inbred population under long and short photoperiods. Our results confirm the importance of the major photoperiod sensitivity locus Hr/PsELF3a and identify two other loci on chromosomes 1 (DTF1) and 3 (DTF3) that contribute to earlier flowering in the domesticated line under both photoperiods. The domesticated allele at a fourth locus on chromosome 6 (DTF6) delays flowering under long days only. Map positions, inheritance patterns, and expression analyses in near-isogenic comparisons imply that DTF1, DTF3, and DTF6 represent gain-of-function alleles of the florigen/antiflorigen genes FTa3, FTa1, and TFL1c/LF, respectively. This echoes similar variation in chickpea and lentil, and suggests a conserved route to reduced photoperiod sensitivity and early phenology in temperate pulses.