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At least 19 recordsLinked to original sources
PubMed1999

Late-flowering genes interact with early-flowering genes to regulate flowering time in Arabidopsis thaliana.

To investigate the genetic mechanisms regulating the transition from the vegetative to reproductive growth in Arabidopsis, double mutants between three different early-flowering mutants, early flowering 1-1, 2-1, 3-1, (elf 1-1, 2-1, 3-1) and five different late-flowering mutants, gi-1, ft-1, fwa-1, ld-1, and fca-9, were constructed and phenotypes analyzed. Double mutants in all combinations displayed the late-flowering phenotypes which resembled their respective late-flowering parents in both flowering time and the number of vegetative leaves produced. The results indicate that five late-flowering mutants are epistatic to all three early-flowering mutants tested here. This epistatic relationship suggests that ELF1, ELF2, and ELF3 genes function upstream of these five late-flowering genes no matter if they are functioning in autonomous or photoperiod pathways. These three early-flowering genes may negatively modify the activity of most late-flowering genes to influence the time of the vegetative-to-reproductive transition in Arabidopsis.

Arabidopsis↗
PubMed2003

Genetic analysis of early flowering mutants in Arabidopsis defines a class of pleiotropic developmental regulator required for expression of the flowering-time switch flowering locus C.

The Arabidopsis flowering-repressor gene FLOWERING LOCUS C (FLC) is a developmental switch used to trigger floral induction after extended growth in the cold, a process termed vernalization. In vernalized plants, FLC becomes transcriptionally silenced through a process that involves an epigenetic mechanism. We identified recessive mutations designated vernalization independence (vip) that confer cold-independent flowering and suppression of FLC. These mutations also lead to developmental pleiotropy, including specific defects in floral morphology, indicating that the associated genes also have functions unrelated to flowering time. We identified the VIP3 gene by positional cloning and found that it encodes a protein consisting almost exclusively of repeated Trp-Asp (WD) motifs, suggesting that VIP3 could act as a platform to assemble a protein complex. Constitutive transgenic expression of VIP3 in vernalized plants is insufficient to activate FLC, and thus VIP3 probably participates in the regulation of FLC as one component of a more extensive mechanism. Consistent with this, genetic analyses revealed that the VIP loci define a functional gene class including at least six additional members. We suggest that VIP3 and other members of this gene class could represent a previously unrecognized flowering mechanism.

Arabidopsis↗
PubMed2003

Arabidopsis TERMINAL FLOWER 2 gene encodes a heterochromatin protein 1 homolog and represses both FLOWERING LOCUS T to regulate flowering time and several floral homeotic genes.

Floral transition should be strictly regulated because it is one of the most critical developmental processes in plants. Arabidopsis terminal flower 2 (tfl2) mutants show an early-flowering phenotype that is relatively insensitive to photoperiod, as well as several other pleiotropic phenotypes. We found that the early flowering of tfl2 is caused mainly by ectopic expression of the FLOWERING LOCUS T (FT) gene, a floral pathway integrator. Molecular cloning of TFL2 showed that it encodes a protein with homology to heterochromatin protein 1 (HP1) of animals and Swi6 of fission yeast. TFL2 protein localizes in subnuclear foci and expression of the TFL2 gene complemented yeast swi6(-) mutants. These results suggested that TFL2 might function as an HP1 in Arabidopsis: Gene expression analyses using DNA microarrays, however, did not show an increase in the expression of heterochromatin genes in tfl2 mutants but instead showed the upregulation of the floral homeotic genes APETALA3, PISTILLATA, AGAMOUS and SEPALLATA3. The pleiotropic phenotype of the tfl2 mutant could reflect the fact that TFL2 represses the expression of multiple genes. Our results demonstrate that despite its homology to HP1, TFL2 is involved in the repression of specific euchromatin genes and not heterochromatin genes in Arabidopsis.

AGAMOUS Protein, Arabidopsis↗
PubMed2004

Repressed ethylene production in the gynoecium of long-lasting flowers of the carnation 'White Candle': role of the gynoecium in carnation flower senescence.

Ethylene production and expression of ethylene biosynthetic genes was investigated in senescing flowers of carnation (Dianthus caryophyllus L.) cultivars 'White Candle (WC)' and 'Light Pink Barbara (LPB)', with long and short vase-lives, respectively. Ethylene production from the gynoecium and petals of senescing 'WC' flowers was below the limit of detection, in agreement with the repressed ethylene production from the whole flowers. However, exogenous ethylene treatment caused the accumulation of transcripts for DC-ACS1 and DC-ACO1 genes in both the gynoecium and petals, resulting in ethylene production from the flowers. Moreover, application of ABA or IAA, which are known to exhibit their action through the induction of ethylene synthesis in the gynoecium, to 'WC' flowers from their cut stem-end induced ethylene production and wilting in the flowers. These findings suggested that, in 'WC' flowers the mechanism of ethylene biosynthesis, i.e. the induction of expression of genes for ethylene biosynthesis and the action of resulting enzymes, was not defective, but that its function was repressed during natural senescence. Transcripts of DC-ACO1, DC-ACS3, and DC-ACS1 were present in the gynoecium of senescing 'LPB' flowers. In the gynoecium of senescing 'WC' flowers, however, the DC-ACO1 transcript was present, but the DC-ACS1 transcript was absent and the DC-ACS3 transcript was detected only in a small amount; the latter two were associated with the low rate of ethylene production in the gynoecium of 'WC' flowers. These findings indicated that the repressed ethylene production in 'WC' flowers during natural senescence is caused by the repressed ethylene production in the gynoecium, giving further support for the role of the gynoecium in regulating petal senescence in carnation flowers.

Abscisic Acid↗
PubMed1974

Isolation of Flower-inducing and Flower-inhibitory Factors from Aphid Honeydew.

The aphid Dactynotus ambrosiae Thomas has been allowed to feed on vegetative or flowering plants of the short-day plant Xanthium strumarium L., and the honeydew which they produce is extracted and tested for an effect on flowering using the long-day plant Lemna gibba L., strain G3 for the bioassay. One zone of flower-inducing activity and at least two zones of flower-inhibitory activity are consistently obtained from the honeydew extracts. The levels of flower-inducing and flower-inhibitory activity are not demonstrably different in vegetative and flowering honeydew. The honeydew extracts are inactive on Xanthium but do give some flower induction with the short-day plant Lemna perpusilla Torr., strain 6746. The flower-inducing activity is clearly of plant origin and is present in the phloem since the same active material can be obtained from vegetative or flowering Xanthium by methanol extraction, and honeydew produced by aphids feeding on a chemically defined synthetic diet is completely without flower-inducing activity. This is the first report of successful flower induction in the long-day plant L. gibba G3 by some means other than long-day treatment.

Journal Article↗
PubMed2005

Role of FRIGIDA and FLOWERING LOCUS C in determining variation in flowering time of Arabidopsis.

Arabidopsis (Arabidopsis thaliana) accessions provide an excellent resource to dissect the molecular basis of adaptation. We have selected 192 Arabidopsis accessions collected to represent worldwide and local variation and analyzed two adaptively important traits, flowering time and vernalization response. There was huge variation in the flowering habit of the different accessions, with no simple relationship to latitude of collection site and considerable diversity occurring within local regions. We explored the contribution to this variation from the two genes FRIGIDA (FRI) and FLOWERING LOCUS C (FLC), previously shown to be important determinants in natural variation of flowering time. A correlation of FLC expression with flowering time and vernalization was observed, but it was not as strong as anticipated due to many late-flowering/vernalization-requiring accessions being associated with low FLC expression and early-flowering accessions with high FLC expression. Sequence analysis of FRI revealed which accessions were likely to carry functional alleles, and, from comparison of flowering time with allelic type, we estimate that approximately 70% of flowering time variation can be accounted for by allelic variation of FRI. The maintenance and propagation of 20 independent nonfunctional FRI haplotypes suggest that the loss-of-function mutations can confer a strong selective advantage. Accessions with a common FRI haplotype were, in some cases, associated with very different FLC levels and wide variation in flowering time, suggesting additional variation at FLC itself or other genes regulating FLC. These data reveal how useful these Arabidopsis accessions will be in dissecting the complex molecular variation that has led to the adaptive phenotypic variation in flowering time.

Amino Acid Sequence↗
PubMed2004

Clonal structure and flowering traits of a bamboo [Phyllostachys pubescens (Mazel) Ohwi] stand grown from a simultaneous flowering as revealed by AFLP analysis.

Abstract Although many bamboo species are characterized by simultaneous flowering at long intervals of up to 120 years, few studies have revealed the length of the flowering interval for very-long-lived bamboo species by observing the whole life cycle of a single clone. The flowering interval of Phyllostachys pubescens had been determined to be 67 years by means of observation through the entire life cycle from 1912 to 1979. We observed and analysed the clonal structure and flowering traits of a P. pubescens community which had regenerated from seed in 1930 and began to flower in 1997. Although this interval was again 67 years, flowering and nonflowering culms were mixed, and the flowering event lasted three years in the community. AFLP analysis of DNA samples showed distinct genets that originated from the previous flowering event and that each genet had its own flowering time. This is the first report to show that (i) different genets are mixed in a community of a large bamboo species with a leptomorphic rhizome system, and (ii) a community that originated from a single flowering event can have a range of flowering years.

Computer Simulation↗
PubMed2003

DETERMINATE and LATE FLOWERING are two TERMINAL FLOWER1/CENTRORADIALIS homologs that control two distinct phases of flowering initiation and development in pea.

Genes in the TERMINAL FLOWER1 (TFL1)/CENTRORADIALIS family are important key regulatory genes involved in the control of flowering time and floral architecture in several different plant species. To understand the functions of TFL1 homologs in pea, we isolated three TFL1 homologs, which we have designated PsTFL1a, PsTFL1b, and PsTFL1c. By genetic mapping and sequencing of mutant alleles, we demonstrate that PsTFL1a corresponds to the DETERMINATE (DET) gene and PsTFL1c corresponds to the LATE FLOWERING (LF) gene. DET acts to maintain the indeterminacy of the apical meristem during flowering, and consistent with this role, DET expression is limited to the shoot apex after floral initiation. LF delays the induction of flowering by lengthening the vegetative phase, and allelic variation at the LF locus is an important component of natural variation for flowering time in pea. The most severe class of alleles flowers early and carries either a deletion of the entire PsTFL1c gene or an amino acid substitution. Other natural and induced alleles for LF, with an intermediate flowering time phenotype, present no changes in the PsTFL1c amino acid sequence but affect LF transcript level in the shoot apex: low LF transcript levels are correlated with early flowering, and high LF transcript levels are correlated with late flowering. Thus, different TFL1 homologs control two distinct aspects of plant development in pea, whereas a single gene, TFL1, performs both functions in Arabidopsis. These results show that different species have evolved different strategies to control key developmental transitions and also that the genetic basis for natural variation in flowering time may differ among plant species.

Amino Acid Sequence↗
PubMed1994

Modification of flower color in florist's chrysanthemum: production of a white-flowering variety through molecular genetics.

Chimeric chalcone synthase (CHS) constructs were prepared in both anti-sense and sense orientations, and introduced into the chrysanthemum cultivar Moneymaker, along with a T-DNA vector lacking a CHS construct. For both the anti-sense and sense constructs, the majority of the plants produced pink flowers typical of Moneymaker itself. Of 133 sense and 83 anti-sense transgenic individuals 3 of each set produced fully white or very pale pink flowers. No white-flowering transgenic plants were obtained in control transformations. The white flowers were found to accumulate higher levels of chalcone synthase precursors and to have reduced levels of chalcone synthase message. A small-scale field trial was performed to evaluate the stability of the phenotype throughout a series of vegetative propagation steps and during plant growth. The white-flowering trait was maintained well through vegetative propagation; however, during growth of individual white-flowering plants, some pink color was found in some flowers. At one site 2% of the white-flowering plants produced a few pink flowers; at two other sites, as many as 10-12% of the plants produced pale pink flowers.

Acyltransferases↗
PubMed2003

SINGLE FLOWER TRUSS regulates the transition and maintenance of flowering in tomato.

The characterisation of the single flower truss ( sft) mutant phenotype of tomato ( Lycopersicon esculentum Mill.), as well as its genetic interactions with other mutations affecting FALSIFLORA ( FA) and SELF PRUNING ( SP) genes, has revealed that SFT is a key gene in the control of floral transition and floral meristem identity. The single sft mutation produces a late-flowering phenotype in both long-day and short-day conditions. In combination with fa, a mutation affecting the tomato gene orthologous to LFY, sft completely blocks the transition to flowering in this species. Thus, the phenotype of the sft fa double mutants indicates that SFT and FA participate in two parallel pathways that regulate the switch from vegetative to reproductive phase in tomato, and that both genes are indispensable for flowering. On the other hand, the replacement of flowers by vegetative shoots observed in the sft inflorescence suggests that SFT regulates flower meristem identity during inflorescence development of tomato. In addition to these two main functions, SFT is involved in the development of both flowers and sympodial shoots of tomato. First, the mutation produces a partial conversion of sepals into leaves in the first floral whorl, and a reduction in the number of floral organs, particularly carpels. Secondly, the sympodial development in the mutant plants is altered, which can be related to the interaction between SFT and SP, a gene controlling the number of nodes in sympodial shoots. In fact, we have found that the sft phenotype is epistatic to that of sp, and that the level of SP mRNA in the apical buds of sft around flowering is reduced. SFT can therefore co-ordinate the regulation of two simultaneous developmental processes in the tomato apical shoot, the promotion of flowering in one sympodial segment and the vegetative development of the next segment.

Arabidopsis Proteins↗
PubMed2000

Tissue-specific oxylipin signature of tomato flowers: allene oxide cyclase is highly expressed in distinct flower organs and vascular bundles.

A crucial step in the biosynthesis of jasmonic acid (JA) is the formation of its correct stereoisomeric precursor, cis(+)12-oxophytodienoic acid (OPDA). This step is catalysed by allene oxide cyclase (AOC), which has been recently cloned from tomato. In stems, young leaves and young flowers, AOC mRNA accumulates to a low level, contrasting with a high accumulation in flower buds, flower stalks and roots. The high levels of AOC mRNA and AOC protein in distinct flower organs correlate with high AOC activity, and with elevated levels of JA, OPDA and JA isoleucine conjugate. These compounds accumulate in flowers to levels of about 20 nmol g-1 fresh weight, which is two orders of magnitude higher than in leaves. In pistils, the level of OPDA is much higher than that of JA, whereas in flower stalks, the level of JA exceeds that of OPDA. In other flower tissues, the ratios among JA, OPDA and JA isoleucine conjugate differ remarkably, suggesting a tissue-specific oxylipin signature. Immunocytochemical analysis revealed the specific occurrence of the AOC protein in ovules, the transmission tissue of the style and in vascular bundles of receptacles, flower stalks, stems, petioles and roots. Based on the tissue-specific AOC expression and formation of JA, OPDA and JA amino acid conjugates, a possible role for these compounds in flower development is discussed in terms of their effect on sink-source relationships and plant defence reactions. Furthermore, the AOC expression in vascular bundles might play a role in the systemin-mediated wound response of tomato.

Cyclopentanes↗
PubMed1993

Flower-bud formation in explants of photoperiodic and day-neutral Nicotiana biotypes and its bearing on the regulation of flower formation.

The capacity to form flower buds in thin-layer explants was studied in flowering plants of several species, cultivars, and lines of Nicotiana differing in their response to photoperiod. This capacity was found in all biotypes examined and could extend into sepals and corolla. It varied greatly, depending on genotype, source tissue and its developmental stage, and composition of the culture medium, particularly the levels of glucose, auxin, and cytokinin. It was greatest in the two day-neutral plants examined, Samsun tobacco and Nicotiana rustica, where it extended from the inflorescence region down the vegetative stem, in a basipetally decreasing gradient; it was least in the two qualitative photoperiodic plants studied, the long-day plant Nicotiana silvestris and the short-day plant Maryland Mammoth tobacco, the quantitative long-day plant Nicotiana alata and the quantitative short-day plant Nicotiana otophora line 38-G-81, where it was limited to the pedicels (and, in some cases, the sepals). Regardless of the photoperiodic response of the source plants, the response was the same in explants cultured under long and short days. The finding that capacity to form flower buds in explants is present in all Nicotiana biotypes studied supports the idea that it is regulated by the same mechanism(s), regardless of the plant's photoperiodic character. However, the source plants were all in the flowering stage, and no flower-bud formation can be obtained in explants from strictly vegetative Nicotiana plants. Hence, flower formation in the explants is not identical with de novo flower formation in a hitherto vegetative plant: it is rather the expression of a floral state already established in the plant, although it can vary widely in extent and spatial distribution. Culture conditions that permit flower-bud formation in an explant are conditions that maintain the floral state and encourage its expression; conditions under which no flower buds are formed reduce this state and/or prevent its expression.

Journal Article↗
PubMed1999

FLOWERING LOCUS C encodes a novel MADS domain protein that acts as a repressor of flowering.

Winter-annual ecotypes of Arabidopsis are relatively late flowering, unless the flowering of these ecotypes is promoted by exposure to cold (vernalization). This vernalization-suppressible, late-flowering phenotype results from the presence of dominant, late-flowering alleles at two loci, FRIGIDA (FRI) and FLOWERING LOCUS C (FLC). In this study, we report that flc null mutations result in early flowering, demonstrating that the role of active FLC alleles is to repress flowering. FLC was isolated by positional cloning and found to encode a novel MADS domain protein. The levels of FLC mRNA are regulated positively by FRI and negatively by LUMINIDEPENDENS. FLC is also negatively regulated by vernalization. Overexpression of FLC from a heterologous promoter is sufficient to delay flowering in the absence of an active FRI allele. We propose that the level of FLC activity acts through a rheostat-like mechanism to control flowering time in Arabidopsis and that modulation of FLC expression is a component of the vernalization response.

Arabidopsis↗
PubMed1999

Trade-offs between flower number and investment to a flower in selfing and outcrossing varieties of Impatiens hypophylla (Balsaminaceae).

Floral resource allocation was compared on a whole-plant basis between two varieties of Impatiens hypophylla that differ in flower size. There were significant negative correlations between flower number and investments to a flower at both the within-population and between-variety levels. In individual flowers, var. hypophylla with larger flowers invested significantly more resources to male and pollinator-attractive functions, whereas investments to female function did not differ between the varieties. In experimental populations placed in the field, pollinators preferred the larger flowers of var. hypophylla even within the same habitat of var. microhypophylla, which has smaller flowers. There was a significant lack of observed heterozygosity only in var. microhypophylla. Thus, the outcrossing variety had more attractive but fewer flowers, while the selfing variety had less attractive but more abundant flowers.

Journal Article↗
PubMed2004

A latitudinal cline in flowering time in Arabidopsis thaliana modulated by the flowering time gene FRIGIDA.

A latitudinal cline in flowering time in accessions of Arabidopsis thaliana has been widely predicted because the environmental cues that promote flowering vary systematically with latitude, but evidence for such clines has been lacking. Here, we report evidence of a significant latitudinal cline in flowering time among 70 Northern European and Mediterranean ecotypes when grown under ecologically realistic conditions in a common garden environment. The detected cline, however, is found only in ecotypes with alleles of the flowering time gene FRIGIDA (FRI) that lack major deletions that would disrupt protein function, whereas there is no relationship between flowering time and latitude of origin among accessions with FRI alleles containing such deletions. Analysis of climatological data suggests that late flowering in accessions with putatively functional FRI was associated with reduced January precipitation at the site of origin, consistent with previous reports of a positive genetic correlation between water use efficiency and flowering time in Arabidopsis, and the pleiotropic effects of FRI of increasing water use efficiency. In accessions collected from Southern latitudes, we detected that putatively functional FRI alleles were associated with accelerated flowering relative to accessions with nonfunctional FRI under the winter conditions of our experiment. These results suggest that the ecological function of the vernalization requirement conferred by FRI differs across latitudes. More generally, our results indicate that by combining ecological and molecular genetic data, it is possible to understand the forces acting on life history transitions at the level of specific loci.

Arabidopsis↗
PubMed2002

A stochastic flowering model describing an asynchronically flowering set of trees.

A general stochastic model is presented that simulates the time course of flowering of individual trees and populations, integrating the synchronization of flowering both between and within trees. Making some hypotheses, a simplified expression of the model, called the 'shoot' model, is proposed, in which the synchronization of flowering both between and within trees is characterized by specific parameters. Two derived models, the 'tree' model and the 'population' model, are presented. They neglect the asynchrony of flowering, respectively, within trees, and between and within trees. Models were fitted and tested using data on flowering of Psidium cattleianum observed at study sites at elevations of 200, 520 and 890 m in Reunion Island. The 'shoot' model fitted the data best and reproduced the strong irregularities in flowering shown by empirical data. The asynchrony of flowering in P. cattleianum was more pronounced within than between trees. Simulations showed that various flowering patterns can be reproduced by the 'shoot' model. The use of different levels of organization of the general model is discussed.

Computer Simulation↗
PubMed2003

Ectopic expression of an orchid (Oncidium Gower Ramsey) AGL6-like gene promotes flowering by activating flowering time genes in Arabidopsis thaliana.

An AP1/AGL9 group of MADS box gene, OMADS1, with extensive homology to the Arabidopsis AGAMOUS-like 6 gene (AGL6) was characterized from orchid (Oncidium Gower Ramsey). OMADS1 mRNA was detected in apical meristem and in the lip and carpel of flower. Yeast two-hybrid analysis indicated that OMADS1 is able to strongly interact with OMADS3, a TM6-like protein that was involved in flower formation and floral initiation in orchid. Transgenic Arabidopsis and tobacco ectopically expressed OMADS1 showed similar novel phenotypes by significantly reducing plant size, flowering extremely early, and losing inflorescence indeterminacy. In addition, homeotic conversion of sepals into carpel-like structures and petals into staminoid structures were also observed in flowers of 35S::OMADS1 Arabidopsis. This result indicated that OMADS1 was involved in floral formation and initiation in transgenic plants. Further analysis indicated that the expression of flowering time genes FT, SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1) and flower meristem identity genes LEAFY (LFY), APETALA1 (AP1) was significantly up-regulated in 35S::OMADS1 transgenic Arabidopsis plants. Furthermore, ectopic expression of OMADS1 rescued late-flowering phenotype in gi-1, co-3 but not for ft-1 and fwa-1 mutants. These results supported that ectopic expression of OMADS1 influenced flower transition and formation by acting as an activator for FT and SOC1 in Arabidopsis.

Amino Acid Sequence↗
PubMed2005

Independent roles for EARLY FLOWERING 3 and ZEITLUPE in the control of circadian timing, hypocotyl length, and flowering time.

The circadian clock regulates many aspects of plant development, including hypocotyl elongation and photoperiodic induction of flowering. ZEITLUPE (ZTL) is a clock-related F-box protein, and altered ZTL expression causes fluence rate-dependent circadian period effects, and altered hypocotyl elongation and flowering time. EARLY FLOWERING 3 (ELF3) is a novel protein of unknown biochemical function. elf3 mutations cause light-dependent circadian dysfunction, elongated hypocotyls, and early flowering. Although both genes affect similar processes, their relationship is unclear. Here we show that the effects of ZTL and ELF3 on circadian clock function and early photomorphogenesis are additive. The long period of ztl mutations and ELF3 overexpressors are more severe than either alone. Dark-release experiments showing additivity in phase advances suggest that the arrthymicity caused by ZTL overexpression and that of the elf3-1 mutation arise through independent pathways. A similar additive effect on hypocotyl elongation in red and blue light is also observed. In contrast, ELF3 and ZTL overexpressors act similarly to control flowering time in long days through the CONSTANS/FLOWERING LOCUS T (CO/FT) pathway. ZTL overexpression does not delay flowering through changes in GIGANTEA or FLAVIN-BINDING, KELCH REPEAT, F-BOX levels, but through a ZTL-mediated reduction in CO expression. In contrast, ELF3 negatively regulates CO, FT, and GIGANTEA transcript levels, as the expression of all three genes is increased in elf3-1. The elf3-1 co-1 double mutant flowers much earlier in long days than co-1, although FT message levels remain very low. These results show that elf3-1 can derepress late flowering through a CO-independent mechanism. ELF3 may act at more than one juncture, possibly posttranscriptionally.

Arabidopsis↗