Floral Meristem Identity Gene LEAFY Research Articles

An Integrative Analysis of Transcriptome, Proteome and Hormones Reveals Key Differentially Expressed Genes and Metabolic Pathways Involved in Flower Development in Loquat.

Flower development is a vital developmental process in the life cycle of woody perennials, especially fruit trees. Herein, we used transcriptomic, proteomic, and hormone analyses to investigate the key candidate genes/proteins in loquat (Eriobotrya japonica) at the stages of flower bud differentiation (FBD), floral bud elongation (FBE), and floral anthesis (FA). Comparative transcriptome analysis showed that differentially expressed genes (DEGs) were mainly enriched in metabolic pathways of hormone signal transduction and starch and sucrose metabolism. Importantly, the DEGs of hormone signal transduction were significantly involved in the signaling pathways of auxin, gibberellins (GAs), cytokinin, ethylene, abscisic acid (ABA), jasmonic acid, and salicylic acid. Meanwhile, key floral integrator genes FLOWERING LOCUS T (FT) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) and floral meristem identity genes SQUAMOSA PROMOTER BINDING LIKE (SPL), LEAFY (LFY), APETALA1 (AP1), and AP2 were significantly upregulated at the FBD stage. However, key floral organ identity genes AGAMOUS (AG), AP3, and PISTILLATA (PI) were significantly upregulated at the stages of FBE and FA. Furthermore, transcription factors (TFs) such as bHLH (basic helix-loop-helix), NAC (no apical meristem (NAM), Arabidopsis transcription activation factor (ATAF1/2) and cup-shaped cotyledon (CUC2)), MYB_related (myeloblastosis_related), ERF (ethylene response factor), and C2H2 (cysteine-2/histidine-2) were also significantly differentially expressed. Accordingly, comparative proteomic analysis of differentially accumulated proteins (DAPs) and combined enrichment of DEGs and DAPs showed that starch and sucrose metabolism was also significantly enriched. Concentrations of GA3 and zeatin were high before the FA stage, but ABA concentration remained high at the FA stage. Our results provide abundant sequence resources for clarifying the underlying mechanisms of the flower development in loquat.

Isolation and Characterization of CsWRKY7, a Subgroup IId WRKY Transcription Factor from Camellia sinensis, Linked to Development in Arabidopsis.

WRKY transcription factors (TFs) containing one or two WRKY domains are a class of plant TFs that respond to diverse abiotic stresses and are associated with developmental processes. However, little has been known about the function of WRKY gene in tea plant. In this study, a subgroup IId WRKY gene CsWRKY7 was isolated from Camellia sinensis, which displayed amino acid sequence homology with Arabidopsis AtWRKY7 and AtWRKY15. Subcellular localization prediction indicated that CsWRKY7 localized to nucleus. Cis-acting elements detected in the promotor region of CsWRKY7 are mainly involved in plant response to environmental stress and growth. Consistently, expression analysis showed that CsWRKY7 transcripts responded to NaCl, mannitol, PEG, and diverse hormones treatments. Additionally, CsWRKY7 exhibited a higher accumulation both in old leaves and roots compared to bud. Seed germination and root growth assay indicated that overexpressed CsWRKY7 in transgenic Arabidopsis was not sensitive to NaCl, mannitol, PEG, and low concentration of ABA treatments. CsWRKY7 overexpressing Arabidopsis showed a late-flowering phenotype under normal conditions compared to wild type. Furthermore, gene expression analysis showed that the transcription levels of the flowering time integrator gene FLOWERING LOCUS T (FT) and the floral meristem identity genes APETALA1 (AP1) and LEAFY (LFY) were lower in WRKY7-OE than in the WT. Taken together, these findings indicate that CsWRKY7 TF may participate in plant growth. This study provides a potential strategy to breed late-blooming tea cultivar.

PERPETUAL FLOWERING2 coordinates the vernalization response and perennial flowering in Arabis alpina.

The floral repressor APETALA2 (AP2) in Arabidopsis regulates flowering through the age pathway. The AP2 ortholog in the alpine perennial Arabis alpina, PERPETUAL FLOWERING 2 (PEP2), was previously reported to control flowering through the vernalization pathway via enhancing the expression of another floral repressor PERPETUAL FLOWERING 1 (PEP1), the ortholog of Arabidopsis FLOWERING LOCUS C (FLC). However, PEP2 also regulates flowering independently of PEP1. To characterize the function of PEP2, we analyzed the transcriptomes of pep2 and pep1 mutants. The majority of differentially expressed genes were detected between pep2 and the wild type or between pep2 and pep1, highlighting the importance of the PEP2 role that is independent of PEP1. Here, we demonstrate that PEP2 activity prevents the up-regulation of the A. alpina floral meristem identity genes FRUITFUL (AaFUL), LEAFY (AaLFY), and APETALA1 (AaAP1), ensuring floral commitment during vernalization. Young pep2 seedlings respond to vernalization, suggesting that PEP2 regulates the age-dependent response to vernalization independently of PEP1. The major role of PEP2 through the PEP1-dependent pathway takes place after vernalization, when it facilitates PEP1 activation both in the main shoot apex and in axillary branches. These multiple roles of PEP2 in the vernalization response contribute to the A. alpina life cycle.

WRKY71 accelerates flowering via the direct activation of FLOWERING LOCUS T and LEAFY in Arabidopsis thaliana.

Flowering is crucial for achieving reproductive success. A large number of well-delineated factors affecting flowering are involved in complex genetic networks in Arabidopsis thaliana. However, the underlying part played by the WRKY transcription factors in this process is not yet clear. Here, we report that WRKY71 is able to accelerate flowering in Arabidopsis. An activation-tagged mutant WRKY71-1D and a constitutive over-expresser of WRKY71 both flowered earlier than the wild type (WT). In contrast, both the RNA interference-based multiple WRKY knock-out mutant (w71w8 + 28RNAi) and the dominant repression line (W71-SRDX) flowered later. Gene expression analysis showed that the transcript abundance of the flowering time integrator gene FLOWERING LOCUS T (FT) and the floral meristem identity genes LEAFY (LFY), APETALA1 (AP1) and FRUITFULL (FUL) were greater in WRKY71-1D than in the WT, but lower in w71w8 + 28RNAi and W71-SRDX. Further, WRKY71 was shown to bind to the W-boxes in the FT and LFY promoters in vitro and in vivo. The suggestion is that WRKY71 activity hastens flowering via the direct activation of FT and LFY.

Effect of extending the photoperiod with low-intensity red or far-red light on the timing of shoot elongation and flower-bud formation of 1-year-old Japanese pear (Pyrus pyrifolia)

To investigate the effects of light quality (wavelength) on shoot elongation and flower-bud formation in Japanese pear (Pyrus pyrifolia (Burm. f.) Nakai), we treated 1-year-old trees with the following: (i) 8 h sunlight + 16 h dark (SD); (ii) 8 h sunlight + 16 h red light (LD(SD + R)); or (iii) 8 h sunlight + 16 h far-red (FR) light (LD(SD + FR)) daily for 4 months from early April (before the spring flush) until early August in 2009 and 2010. In both years, shoot elongation stopped earlier in the LD(SD + FR) treatment than in the SD and LD(SD + R) treatments. After 4 months of treatments, 21% (2009) or 40% (2010) of LD(SD + FR)-treated trees formed flower buds in the shoot apices, whereas all the shoot apices from SD or LD(SD + R)-treated plants remained vegetative. With an additional experiment conducted in 2012, we confirmed that FR light at 730 nm was the most efficacious wavelength to induce flower-bud formation. Reverse transcription-quantitative polymerase chain reaction revealed that the expression of two floral meristem identity gene orthologues, LEAFY (PpLFY2a) and APETALA1 (PpMADS2-1a), were up-regulated in the shoot apex of LD(SD + FR). In contrast, the expression of a flowering repressor gene, TERMINAL FLOWER 1 (PpTFL1-1a, PpTFL1-2a), was down-regulated. In addition, expression of an orthologue of the flower-promoting gene FLOWERING LOCUS T (PpFT1a) was positively correlated with flower-bud formation, although the expression of another orthologue, PpFT2a, was negatively correlated with shoot growth. Biologically active cytokinin and gibberellic acid concentrations in shoot apices were reduced with LD(SD + FR) treatment. Taken together, our results indicate that pear plants are able to regulate flowering in response to the R : FR ratio. Furthermore, LD(SD + FR) treatment terminated shoot elongation and subsequent flower-bud formation in the shoot apex at an earlier time, possibly by influencing the expression of flowering-related genes and modifying plant hormone concentrations.

Interlocking Feedback Loops Govern the Dynamic Behavior of the Floral Transition inArabidopsis

During flowering, primordia on the flanks of the shoot apical meristem are specified to form flowers instead of leaves. Like many plants, Arabidopsis thaliana integrates environmental and endogenous signals to control the timing of reproduction. To study the underlying regulatory logic of the floral transition, we used a combination of modeling and experiments to define a core gene regulatory network. We show that FLOWERING LOCUS T (FT) and TERMINAL FLOWER1 (TFL1) act through FD and FD PARALOG to regulate the transition. The major floral meristem identity gene LEAFY (LFY) directly activates FD, creating a positive feedback loop. This network predicts flowering behavior for different genotypes and displays key properties of the floral transition, such as signal integration and irreversibility. Furthermore, modeling suggests that the control of TFL1 is important to flexibly counterbalance incoming FT signals, allowing a pool of undifferentiated cells to be maintained despite strong differentiation signals in nearby cells. This regulatory system requires TFL1 expression to rise in proportion to the strength of the floral inductive signal. In this network, low initial levels of LFY or TFL1 expression are sufficient to tip the system into either a stable flowering or vegetative state upon floral induction.

A conserved domain in the N‐terminus is important for LEAFY dimerization and function in Arabidopsis thaliana

The floral meristem identity gene LEAFY (LFY) of Arabidopsis thaliana is essential for the formation of fertile flowers and has roles in the control of several aspects of floral development, which include phyllotaxy and organ number and identity. This gene encodes a land plant-specific transcription factor and regulates expression of a number of genes that include other floral meristem identity genes and floral homeotic genes. Although the LFY DNA-binding domain has a structure that resembles that of helix-turn-helix proteins, LFY and its orthologs represent a novel family of transcription factors that are characterized by a conserved N-terminus domain of unknown function and a C-terminus DNA-binding domain. Many transcription factors act as dimers. These dimers are essential for the biological activity of the proteins. We demonstrate that LFY forms homodimers or oligomers in solution. This association is mediated through the N-terminus conserved region of the LFY protein. Although mutant LFY proteins that cannot dimerize in solution can bind DNA, the binding is weaker than that of wild type LFY protein. LFY-LFY interactions mediated by the N-terminus domain are essential for the biological activity of this protein, as mutations that abolish the ability to self-associate cannot complement an lfy null allele. Our data indicate: (i) that LFY, and probably its orthologs in other plants, must act in complexes that contain at least two LFY molecules; and (ii) that the N-terminus is essential for stabilization of LFY complexes. This situation is integral to the ability of LFY to regulate gene expression.

A Gain‐of‐Function Mutation in IAA7/AXR2 Confers Late Flowering under Short‐day Light in ArabidopsisF

Floral initiation is a major step in the life cycle of plants, which is influenced by photoperiod, temperature, and phytohormones, such as gibberellins (GAs). It is known that GAs promote floral initiation under short-day light conditions (SDs) by regulating the floral meristem-identity gene LEAFY (LFY) and the flowering-time gene SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1). We have defined the role of the auxin signaling component INDOLE-3-ACETIC ACID 7 (IAA7)/AUXIN RESISTANT 2 (AXR2) in the regulation of flowering time in Arabidopsis thaliana. We demonstrate that the gain-of-function mutant of IAA7/AXR2, axr2-1, flowers late under SDs. The exogenous application of GAs rescued the late flowering phenotype of axr2-1 plants. The expression of the GA20 oxidase (GA20ox) genes, GA20ox1 and GA20ox2, was reduced in axr2-1 plants, and the levels of both LFY and SOC1 transcripts were reduced in axr2-1 mutants under SDs. Furthermore, the overexpression of SOC1 or LFY in axr2-1 mutants rescued the late flowering phenotype under SDs. Our results suggest that IAA7/AXR2 might act to inhibit the timing of floral transition under SDs, at least in part, by negatively regulating the expressions of the GA20ox1 and GA20ox2 genes.

Quantitative expression analysis of meristem identity genes in Eucalyptus occidentalis: AP1 is an expression marker for flowering

A number of Eucalyptus species exhibit precocious flowering, flowering within a year of germination and often while still exhibiting juvenile foliage. To understand the nature of precocious flowering in Eucalyptus occidentalis, partial homologues of the inflorescence meristem identity gene TERMINAL FLOWER1 and of the floral meristem identity genes LEAFY and APETALA1 (EOTFL1, EOLFY and EOAP1, respectively) were isolated and characterized. The expression patterns of these meristem identity genes during the development of branched and single-stem plants were analysed by quantitative reverse transcriptase PCR. All E. occidentalis plants commenced flowering within 40 weeks of germination. However, the branched plants reached maximum flowering some 5-6 weeks earlier than did single-stem plants. Levels of EOTFL1 and EOLFY expression varied little during the study period irrespective of architecture treatment, whereas expression of EOAP1 reached a peak coincident with peak flowering in both branched and single-stem plants. AP1 is clearly an expression marker for flowering in this species.

The histone acetyltransferase GCN5 affects the inflorescence meristem and stamen development in Arabidopsis

A central question in biology is to understand how gene expression is precisely regulated to give rise to a variety of forms during the process of development. Epigenetic effects such as DNA methylation or histone modification have been increasingly shown to play a critical role in regulation of genome function. GCN5 is a prototypical histone acetyltransferase that participates in regulating developmental gene expression in several metazoan species. In Arabidopsis thaliana, plants with T-DNA insertions in GCN5 (also known as HAG1) display a variety of pleiotropic effects including dwarfism, loss of apical dominance, and floral defects affecting fertility. We sought to determine when during early development floral abnormalities first arise. Using scanning electron microscopy, we demonstrate that gcn5-1/hag1-1 and gcn5-5/hag1-5 mutants display overproliferation of young buds and development of abnormal structures around the inflorescence meristem. gcn5 mutants also display defects in stamen number and arrangement at later stages. This analysis provides temporal and spatial information to aid in the identification of GCN5 target genes in the developing flower. Preliminary studies of putative targets using reverse transcriptase PCR suggest that the floral meristem identity gene LEAFY is among factors upregulated in gcn5-1 mutants.

Overexpression of AtLEAFY Accelerates Flowering in Brassica juncea

The floral meristem identity gene LEAFY (LFY) from Arabidopsis thaliana (L.) Heynh. can accelerate flowering in dicotyledonous plants. In this report, we raised transgenic plants of Brassica juncea (L.) Czern. cv. Varuna carrying the LEAFY gene (LFY) in sense and antisense orientation and studied the effect of modulation of LFY expression on flowering. The time required for the initiation of flowering was found to be reduced by 19% (∼1 wk earlier) in the transgenic plants overexpressing LFY as compared with the wild‐type untransformed control plants. Moreover, no significant yield penalty was observed in these transgenic plants. Altogether, these results open up the possibility of manipulating the flowering time in B. juncea without significant yield penalty or abnormalities.

Nonflowers near the base of extant angiosperms? Spatiotemporal arrangement of organs in reproductive units of Hydatellaceae and its bearing on the origin of the flower

Reproductive units (RUs) of Trithuria, the sole genus of the early-divergent angiosperm family Hydatellaceae, are compared with flowers of their close relatives in Cabombaceae (Nymphaeales). Trithuria RUs combine features of flowers and inflorescences. They differ from typical flowers in possessing an "inside-out" morphology, with carpels surrounding stamens; furthermore, carpels develop centrifugally, in contrast to centripetal or simultaneous development in typical flowers. Trithuria RUs could be interpreted as pseudanthia of two or more cymose partial inflorescences enclosed within an involucre, but the bractlike involucral phyllomes do not subtend partial inflorescences and hence collectively resemble a typical perianth. Teratological forms of T. submersa indicate a tendency to fasciation and demonstrate that the inside-out structure-the primary feature that separates RUs of Hydatellaceae from more orthodox angiosperm flowers-can be at least partially modified, thus producing a morphology that is closer to an orthodox flower. The Trithuria RU could be described as a "nonflower", i.e., a structure that contains typical angiosperm carpels and stamens but does not allow recognition of a typical angiosperm flower. The term nonflower could combine cases of secondary loss of flower identity and cases of a prefloral condition, similar to those that gave rise to the angiosperm flower. Nonhomology among some angiosperm flowers could be due to iterative shifts between nonfloral construction and flower/inflorescence organization of reproductive organs. Potential testing of these hypotheses using evolutionary-developmental genetics is explored using preliminary data from immunolocalization of the floral meristem identity gene LEAFY in T. submersa, which indicated protein expression at different hierarchical levels.

Molecular markers and a sequence deletion in intron 2 of the putative partial homologue of LEAFY reveal geographical structure to genetic diversity in the acutely threatened legume genus Clianthus

Clianthus is an acutely threatened, bird-pollinated genus endemic to New Zealand, represented in the wild by only one population of C. puniceus and 11 populations of C. maximus, each with very few individuals (typically <10 per population). A limited number of named Clianthus cultivars of indeterminate origin are commonly grown as ornamentals. Genomic DNA from individual Clianthus plants was extracted for genetic diversity analysis using a range of molecular markers, including amplified fragment length polymorphism (AFLP). Data were analysed by the unweighted pair-group method with arithmetic averaging (UPGMA), the generation of Neighbor-Joining trees, and analyses of molecular variance (AMOVA). Genetic distance between wild populations of C. maximus was highly correlated with geographical distance between populations. Sequencing of intron 2 of a putative partial homologue of the floral meristem identity gene LEAFY ( CmLFY) revealed a 7 bp deletion that was exhibited homozygously in the more northern populations of C. maximus, and in all individuals tested from the sole population of C. puniceus. This deletion was not exhibited in more southern populations of C. maximus. Further, one geographically intermediate population contained some plants that were heterozygous for the deletion. Parallel analyses of cultivated Clianthus genotypes, more than half of which were also homozygous for the 7 bp deletion, showed that these were not representative of the broad, but threatened, diversity remaining in the wild. It is argued that wild populations of C. maximus are unlikely to have arisen from the escape of plants from cultivation. Conservation effort should focus on the protection and study of the extant plants in these wild populations, rather than on the introduction of disturbance regimes to uncover potential seed banks.

AGAMOUS‐LIKE 17, a novel flowering promoter, acts in a FT‐independent photoperiod pathway

The photoperiod pathway is a genetically conserved pathway that affects flowering in distantly related angiosperms. Here we report a novel flowering promoter AGAMOUS-LIKE 17 (AGL17) acting in the photoperiod pathway of Arabidopsis. AGL17 transcripts were detectable in various plant organs with the highest expression in the root. Under long-day conditions, expression of AGL17 gradually increased in the aerial part of seedlings during the floral transition. Overexpression of AGL17 caused early flowering, while loss of function of AGL17 exhibited late flowering, particularly under long days. Analysis of AGL17 expression in various flowering-time mutants showed that its transcripts were significantly reduced in the photoperiod pathway mutant co-1. Correspondingly, AGL17 expression was upregulated in transgenic plants overexpressing CONSTANS (CO) and also when CO activity was induced by light. Genetic analysis further showed that overexpression of AGL17 could partially suppress the late flowering of co-1. These results suggest that AGL17 acts to promote flowering and is positively controlled by the photoperiod pathway regulator CO. In contrast, another target of CO, FLOWERING LOCUS T (FT), did not affect AGL17 expression, and vice versa. The expression of two floral meristem identity genes LEAFY (LFY) and APETALA1 (AP1) decreased in agl17-1, while LFY and AP1 could be rapidly induced by AGL17 using a functional estradiol-inducible system. These findings indicate that AGL17 ultimately promotes flowering via regulation of LFY and AP1.

RsLFY, a LEAFY homologue gene in radish (Raphanus sativus), is continuously expressed in vegetative, reproductive and seed development

The floral meristem identity gene LEAFY (LFY) in Arabidopsis plays a key role in flower development. We isolated two LFY-like genes from radish, designated RsLFY1 and RsLFY2. Comparison of genomic and cDNA sequences revealed that the number and positions of introns are precisely conserved in RsLFY1, RsLFY2 and LFY. Using RsLFY1 full- length cDNA as a probe, genomic DNA blot hybridization analysis detected two hybridizing fragments under high stringency, suggesting that there are two RsLFY loci within radish genome. Both genes were expressed during vegetative growth, reproductive growth, flower development and seed development. RsLFY1 was expressed slightly in leaf primordia and strongly in early floral meristem. It was expressed successively in primordia of sepals, petals, stamens, gynoecium, ovule integument and mature seeds. These results suggest that RsLFY1 plays a similar role to LFY in floral initiation and the developmental stages of floral organs, and that it also may regulate radish seed development, unlike LFY.

Specification ofArabidopsisfloral meristem identity by repression of flowering time genes

Flowering plants produce floral meristems in response to intrinsic and extrinsic flowering inductive signals. In Arabidopsis, the floral meristem identity genes LEAFY (LFY) and APETALA1 (AP1) are activated to play a pivotal role in specifying floral meristems during floral transition. We show here that the emerging floral meristems require AP1 to partly specify their floral identities by directly repressing a group of flowering time genes, including SHORT VEGETATIVE PHASE (SVP), AGAMOUS-LIKE 24 (AGL24) and SUPPRESSOR OF OVEREXPRESSION OF CO1 (SOC1). In wild-type plants, these flowering time genes are normally downregulated in emerging floral meristems. In the absence of AP1, these genes are ectopically expressed, transforming floral meristems into shoot meristems. By post-translational activation of an AP1-GR fusion protein and chromatin immunoprecipitation assays, we further demonstrate the repression of these flowering time genes by induced AP1 activity and in vivo AP1 binding to the cis-regulatory regions of these genes. These findings indicate that once AP1 is activated during the floral transition, it acts partly as a master repressor in floral meristems by directly suppressing the expression of flowering time genes, thus preventing the continuation of the shoot developmental program.

Morphological and molecular analyses of the tomato floral mutant leafy inflorescence, a new allele of falsiflora

The purpose of this study was to advance understanding of the molecular mechanisms of tomato floral development that differ from those of Arabidopsis, through morphological and molecular biological analyses of the tomato floral mutant leafy inflorescence ( lfi). In lfi inflorescences, shoot apex-like meristems have indeterminate growth and develop into large leafy inflorescence that fail to flower. A 12 bp deletion was found in the 3′ region of the open reading frame of FALSIFLORA ( FA), the tomato ortholog of the Arabidopsis floral meristem identity gene LEAFY, in the lfi mutant. An allelism test indicated that lfi is allelic to falsiflora. Because the FA locus controls floral meristem identity, expression analyses of several floral organ identity genes were carried out to deduce the relationship between these genes and FA. Expression of the tomato floral organ identity genes TDR6 and TAG1 was inhibited in lfi inflorescences, suggesting that FA induces tomato floral organ identity genes, as LEAFY does in Arabidopsis. In addition, FA promoted the induction of the SEP3 ortholog, TDR5, although TDR4 was not regulated by FA. The investigation of ectopic carpel formation, a unique feature of lfi, suggested that TAG1 (a group C gene) and TDR5 have important roles in carpel formation, as in Arabidopsis. However, the expression of TDR6, which is thought to be a group B gene, is also associated with ectopic carpel formation, unlike in Arabidopsis.

Isolation and Characterization of LEAFY and APETALA1 Homologues from Citrus sinensis L. Osbeck `Washington'

Homologues of the floral meristem identity genes LEAFY (LFY) and APETALA1 (AP1) were isolated from the hybrid perennial tree crop `Washington' navel orange (Citrus sinensis) and designated CsLFY and CsAP1, respectively. Citrus has an extended juvenile period unlike herbaceous plants and responds to different floral stimuli than herbaceous plants or deciduous tree species. Despite these differences, the deduced amino acid sequences of CsLFY and CsAP1 genes are at least 65% identical with their Arabidopsis thaliana L. Heynh counterparts and share even greater sequence similarity to LFY and AP1 from the deciduous woody perennials, Populus balsamifera Bradshaw and Populus tremuloides Michaux, respectively. Like A. thaliana LFY (AtLFY) and AP1 (AtAP1), CsLFY and CsAP1 expression was restricted almost exclusively to reproductive tissues, but observed expression of CsAP1 in the fourth whorl carpel tissue of mature flowers was distinct from other plant AP1 genes. Transgenic A. thaliana plants ectopically expressing CsLFY or CsAP1 showed early-flowering phenotypes similar to those described for overexpression of AtLFY and AtAP1. In addition, the 35S:CsLFY and 35S:CsAP1 transgenes partially complemented the lfy-10 and ap1-3 mutants, respectively. The severity of the overexpression phenotypes correlated with the accumulation of CsLFY or CsAP1 transcripts. LFY is a single-copy gene in flowering plants but consistent with its hybrid origin, the genome of C. sinensis `Washington' has two easily distinguishable CsLFY and CsAP1 alleles derived from it's parental genotypes, C. maxima L. Osbeck (pummelo) and C. reticulata Blanco (mandarin). Allelic polymorphism at both the CsLFY and CsAP1 loci was restricted to the 5′- and 3′-flanking regions.

MdTFL1, a TFL1-like gene of apple, retards the transition from the vegetative to reproductive phase in transgenic Arabidopsis

Unlike herbaceous plants, fruit trees such as the apple ( Malus × domestica Borkh.) flower and set fruit only after an extended juvenile phase lasting several years. While studying juvenility in apple trees, we cloned Malus domestica TFL1 ( MdTFL1), a gene homologous to TERMINAL FLOWER 1 ( TFL1) that suppresses the floral meristem identity genes LEAFY ( LFY) and APETALA1 ( AP1) and maintains the inflorescence meristem in Arabidopsis. MdTFL1 mRNA was expressed preferentially in apple vegetative tissues such as apical buds, stems and roots of seedlings, and expression peaked in early July in apical buds, about two weeks prior to floral bud differentiation. Transgenic Arabidopsis expressing MdTFL1 flowered noticeably later than wild-type plants and exhibited a phenotype similar to that of transgenic Arabidopsis overexpressing TFL1. These results suggest that MdTFL1 is involved in the maintenance of the vegetative phase in apple and that it functions analogously to TFL1.

EgLFY, the Eucalyptus grandis homolog of the Arabidopsis gene LEAFY is expressed in reproductive and vegetative tissues

The EgLFY gene cloned from Eucalyptus grandis has sequence homology to the floral meristem identity gene LEAFY (LFY) from Arabidopsis and FLORICAULA (FLO) from Antirrhinum. EgLFY is preferentially expressed in the developing eucalypt floral organs in a pattern similar to that described previously for the Arabidopsis LFY. In situ hybridization experiments have shown that EgLFY is strongly expressed in the early floral meristem and then successively in the primordia of sepals, petals, stamens and carpels. It is also expressed in the leaf primordia of adult trees. The expression of the EgLFY coding region under control of the Arabidopsis LFY promoter could complement strong lfy mutations in transgenic Arabidopsis plants. These data suggest that EgLFY plays a similar role to LFY in flower development and that the basic mechanisms involved in flower initiation and development in Eucalyptus may be similar to those occurring in Arabidopsis.