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PubMed1990

Influence of water deficits on the abscisic Acid and indole-3-acetic Acid contents of cotton flower buds and flowers.

A field experiment was conducted during the summer of 1988 to test the hypothesis that water deficit affects the abscisic acid (ABA) and indole acetic acid (IAA) concentrations in cotton (Gossypium hirsutum L.) flower buds in ways that predispose young fruits (bolls) that subsequently develop from them to increased abscission rates. Water deficit had little effect on the ABA content of flower buds but increased the ABA content of flowers as much as 66%. Water deficit decreased the concentrations of free and conjugated IAA in flower buds during the first irrigation cycle but increased them during the second cycle. Flowers contained much less IAA than buds. Water deficit slightly increased the conjugated IAA content of flowers but had no effect on the concentration of free IAA in flowers. Because water deficit slightly increased the ABA content but did not decrease the IAA content of flowers, any carry-over effect of water deficit on young boll shedding might have been caused by changes in ABA but not from changes in IAA.

Journal Article↗

PubMed2006

Analysis of the volatiles emitted by whole flowers and isolated flower organs of the carob tree using HS-SPME-GC/MS.

The volatiles emitted by fresh whole flowers and isolated flower organs of male, female, and hermaphrodite carob trees (Ceratonia siliqua L.; Leguminosae) were analyzed by headspace solid-phase microextraction followed by capillary gas chromatography and mass spectrometry. The headspace of carob flowers is mainly constituted of high amounts of monoterpenes and sesquiterpenes, and more than 25 compounds were identified. The gender and cultivar affected both the qualitative profile and the relative abundances of the volatiles of whole flowers and isolated floral organs. Linalool and its derivatives (cis-linalool furan oxide, 2,2,6-trimethyl-3-keto-6-vinyltetrahydropyran, cis-linalool pyran oxide, and trans-linalool furan oxide), alpha-pinene, and alpha-farnesene were the dominant volatiles. Female flowers had a higher diversity of volatile compounds than males and hermaphrodites, but a lower abundance of the major ones. Similarly, the floral scent of female flowers of cv. Mulata had a higher content of volatiles but a lower abundance of the major ones, when compared to cv. Galhosa. In each of the three gender types of flowers, the nectary disks seemed to be the major source of volatiles.

Fabaceae↗

PubMed2026

The Jumonji C domain-containing proteins GmJMJ19 and GmJMJ20 link florigen signaling with epigenetic regulation of photoperiodic flowering and post-flowering plant height in soybean.

Soybean (Glycine max) is a photoperiod-sensitive legume whose latitudinal adaptation depends on the precise control of flowering time and plant height. Histone demethylases of the JmjC domain-containing (JMJ) protein family have been implicated in these processes across plant species, but their specific roles in soybean remain largely unexplored. Here, we identify soybean GmJMJ19 and GmJMJ20, two closely related JMJD5/KDM8 orthologs, as master epigenetic regulators that coordinately control both photoperiodic flowering and post-flowering plant height. Both genes exhibit intrinsic, rhythmic expression peaking at ZT12, and their encoded proteins physically interact with the florigen proteins FT2a and FT5a. Loss-of-function mutants display delayed flowering under long days (LDs) and increased plant height under both LDs and short days (SDs), whereas overexpression phenocopies the mutant flowering phenotype, indicating revealing a critical dosage requirement for proper function. Mechanistically, GmJMJ19 and GmJMJ20 are recruited by the FT/FD transcriptional complex to directly activate AP1a and AP1c expression through chromatin modulation. Population genomic analyses reveal distinct selection signatures: GmJMJ19 underwent sustained directional selection during cultivation, whereas GmJMJ20 experienced an early domestication sweep with limited subsequent change. Haplotype analysis identifies coordinated latitudinal clines, with the JMJ19H1/JMJ20H1 combination predominating at high latitudes to promote early flowering and limit height, while JMJ19H2/JMJ20H2 and wild JMJ19H3/JMJ20H3 alleles prevail at low latitudes, conferring later flowering and increased height. Collectively, our findings establish GmJMJ19 and GmJMJ20 as central chromatin regulators linking florigen signaling to downstream target expression and provide valuable allelic resources for breeding regionally adapted soybean varieties across a wide range of latitudinal environments.

Histone modulation↗

PubMed2005

Phytochrome B in the mesophyll delays flowering by suppressing FLOWERING LOCUS T expression in Arabidopsis vascular bundles.

Light is one of the most important environmental factors that determine the timing of a plant's transition from the vegetative to reproductive, or flowering, phase. Not only daylength but also the spectrum of light greatly affect flowering. The shade of nearby vegetation reduces the ratio of red to far-red light and can trigger shade avoidance responses, including stem elongation and the acceleration of flowering. Phytochrome B (phyB) acts as a photoreceptor for this response. Physiological studies have suggested that leaves can perceive and respond to shade. However, little is known about the mechanisms involved in the processing of light signals within leaves. In this study, we used an enhancer-trap system to establish Arabidopsis thaliana transgenic lines that express phyB-green fluorescent protein (GFP) fusion protein in tissue-specific manners. The analysis of these lines demonstrated that phyB-GFP in mesophyll cells affected flowering, whereas phyB-GFP in vascular bundles did not. Furthermore, mesophyll phyB-GFP suppressed the expression of a key flowering regulator, FLOWERING LOCUS T, in the vascular bundles of cotyledons. Hence, a novel intertissue signaling from mesophyll to vascular bundles is revealed as a critical step for the regulation of flowering by phyB.

Arabidopsis↗

PubMed2005

The nuclear actin-related protein ARP6 is a pleiotropic developmental regulator required for the maintenance of FLOWERING LOCUS C expression and repression of flowering in Arabidopsis.

Actin-related proteins (ARPs) are found in the nuclei of all eukaryotic cells, but their functions are generally understood only in the context of their presence in various yeast and animal chromatin-modifying complexes. Arabidopsis thaliana ARP6 is a clear homolog of other eukaryotic ARP6s, including Saccharomyces cerevisiae ARP6, which was identified as a component of the SWR1 chromatin remodeling complex. We examined the subcellular localization, expression patterns, and loss-of-function phenotypes for this protein and found that Arabidopsis ARP6 is localized to the nucleus during interphase but dispersed away from the chromosomes during cell division. ARP6 expression was observed in all vegetative tissues as well as in a subset of reproductive tissues. Null mutations in ARP6 caused numerous defects, including altered development of the leaf, inflorescence, and flower as well as reduced female fertility and early flowering in both long- and short-day photoperiods. The early flowering of arp6 mutants was associated with reduced expression of the central floral repressor gene FLOWERING LOCUS C (FLC) as well as MADS AFFECTING FLOWERING 4 (MAF4) and MAF5. In addition, arp6 mutations suppress the FLC-mediated late flowering of a FRIGIDA-expressing line, indicating that ARP6 is required for the activation of FLC expression to levels that inhibit flowering. These results indicate that ARP6 acts in the nucleus to regulate plant development, and we propose that it does so through modulation of chromatin structure and the control of gene expression.

Actins↗

PubMed2001

Identification of a MADS-box gene, FLOWERING LOCUS M, that represses flowering.

The timing of flowering is important for the reproductive success of plants. Here we describe the identification and characterization of a new MADS-box gene, FLOWERING LOCUS M (FLM), which is involved in the transition from vegetative to reproductive development. FLM is similar in amino-acid sequence to FLC, another MADS-box gene involved in flowering-time control. flm mutants are early flowering in both inductive and non-inductive photoperiods, and flowering time is sensitive to FLM dosage. FLM overexpression produces late-flowering plants. Thus FLM acts as an inhibitor of flowering. FLM is expressed in areas of cell division such as root and shoot apical regions and leaf primordia.

Amino Acid Sequence↗

PubMed1973

Flower Formation in Excised Tobacco Stem Segments: III. Deoxyribonucleic Acid Content in Stem Tissue of Vegetative and Flowering Tobacco Plants.

A method has been developed that extracts DNA from stem tissue of flowering tobacco plants, Nicotiana tabacum cv. Wis. 38. The DNA content of stem tissue from a flowering tobacco plant is correlated with its capacity to flower in vitro. Stem segments known to form 100% floral buds contain 10 times more DNA per gram fresh weight than segments that form 5% floral buds and 95% vegetative buds, and in the uppermost 28 centimeters of flowering tobacco plant stems the DNA content decreases roughly in parallel with the floral gradient.((3)H)-Thymidine incorporation into DNA in the internodes is inhibited by attached leaves in flowering tobacco plants but promoted in vegetative plants. Low indoleacetic acid concentrations (2.8 and 5.7 mum) inhibit DNA synthesis in internodes of defoliated stems of flowering tobacco plants to the same extent as attached leaves, whereas the same concentrations of indoleacetic acid promote DNA synthesis in internodes of defoliated stems of vegetative plants. The optimal concentration (11.4 mum) of indoleacetic acid supplied to defoliated stems of vegetative plants increased the rate of DNA synthesis to 4 times the rate in defoliated stems without indoleacetic acid treatment. This increase more than compensates for the promotion of DNA synthesis by the young leaves. Thus, the opposite effects of young leaves on DNA synthesis in internodes of flowering and vegetative tobacco plants may be related to their auxin content.

Journal Article↗

PubMed2001

Loss of FLOWERING LOCUS C activity eliminates the late-flowering phenotype of FRIGIDA and autonomous pathway mutations but not responsiveness to vernalization.

The MADS domain--containing transcription factor FLOWERING LOCUS C (FLC) acts as an inhibitor of flowering and is a convergence point for several pathways that regulate flowering time in Arabidopsis. In naturally occurring late-flowering ecotypes, the FRIGIDA (FRI) gene acts to increase FLC levels, whereas the autonomous floral promotion pathway and vernalization act to reduce FLC expression. Previous work has shown that the Landsberg erecta allele of FLC, which is not a null allele, is able to partially suppress the late-flowering phenotype of FRIGIDA and mutations in the autonomous pathway. In this study, using a null allele of FLC, we show that the late-flowering phenotype of FRIGIDA and autonomous pathway mutants are eliminated in the absence of FLC activity. In addition, we have found that the downregulation of SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 by FRI and autonomous pathway mutants also is mediated by FLC. Complete loss of FLC function, however, does not eliminate the effect of vernalization. Thus, FRI and the autonomous pathway may act solely to regulate FLC expression, whereas vernalization is able to promote flowering via FLC-dependent and FLC-independent mechanisms.

Arabidopsis↗

PubMed1999

The Arabidopsis FILAMENTOUS FLOWER gene is required for flower formation.

A screen for mutations affecting flower formation was carried out and several filamentous flower (fil) alleles were identified. In fil mutants, floral primordia occasionally give rise to pedicels lacking flowers at their ends. This defect is dramatically enhanced in fil rev double mutants, in which every floral primordium produces a flowerless pedicel. These data suggest that the FIL and REV genes are required for an early step of flower formation, possibly for the establishment of a flower-forming domain within the floral primordium. The FIL gene is also required for establishment of floral meristem identity and for flower development. During flower development, the FIL gene is required for floral organ formation in terms of the correct numbers and positions; correct spatial activity of the AGAMOUS, APETALA3, PISTILLATA and SUPERMAN genes; and floral organ development.

AGAMOUS Protein, Arabidopsis↗

PubMed2006

Delayed flowering time in Arabidopsis and Brassica rapa by the overexpression of FLOWERING LOCUS C (FLC) homologs isolated from Chinese cabbage (Brassica rapa L.: ssp. pekinensis).

Chinese cabbage plants remain in the vegetative growth phase until they have experienced prolonged exposure to cold temperature, known as vernalization. This inhibition of flowering is caused by the high levels of FLOWERING LOCUS C (FLC) expression. To increase the product value of Chinese cabbage by inhibiting the floral transition, three genes (BrFLC1, BrFLC2, and BrFLC3) homologous to the AtFLC gene, which encodes a floral repressor, were isolated from the Chinese cabbage 'Chiifu'. These genes showed high similarity to AtFLC, although the putative BrFLC1 protein contained ten more residues than AtFLC. The BrFLC genes were expressed ubiquitously, except that BrFLC3 was not expressed in roots. BrFLC1 and BrFLC2 showed stronger expression than BrFLC3 in unvernalized and vernalized Chinese cabbage. The expression levels of the three BrFLC genes were lower in an early-flowering Chinese cabbage, suggesting that the BrFLC transcript level was associated with flowering time. Constitutive expression of the BrFLC genes in Arabidopsis significantly delayed flowering, which was also observed in transgenic Chinese cabbage overexpressing BrFLC3. These results suggest that the BrFLC genes act similarly to AtFLC. Our results provide a technique for controlling flowering time in Chinese cabbage and other crops to produce high yields of vegetative tissues.

Amino Acid Sequence↗

PubMed2005

Delay in flowering and increase in biomass of transgenic tobacco expressing the Arabidopsis floral repressor gene FLOWERING LOCUS C.

FLOWERING LOCUS C (FLC), a gene from Arabidopsis thaliana (L.) Heynh. that acts as a flowering repressor, was expressed in tobacco (Nicotiana tabacum L. 'Samsun'). Five putative transgenic lines were selected and examined for the presence of FLC. Genomic DNA and total RNA were isolated from the Leaves and used for polymerase chain reaction (PCR) and RNA blot analysis, respectively. Both DNA and RNA tests confirmed the integration and transcription of FLC in all five Lines and their T1 progenies. Transgenic plants in one Line showed an average of 36 d delay in flowering time compared to control plants, and the overall mean for all lines was 14 d. Transgenic plants also displayed increased leaf size and biomass yield and reduced height at flowering time. It is important to note that the delay in flowering might have been caused by a slower rate of leaf initiation (i.e. nodes/day) rather than by a change in the flowering mechanism itself.

Arabidopsis Proteins↗

PubMed2005

Prevention of early flowering by expression of FLOWERING LOCUS C requires methylation of histone H3 K36.

Flowering represents a crucial transition from a vegetative to a reproductive phase of the plant life cycle. Despite extensive studies, the molecular mechanisms controlling flowering remain elusive. Although the enzymes involved are unknown, methylation of histone H3 K9 and K27 correlates with repression of FLOWERING LOCUS C (FLC), an essential transcriptional repressor involved in flowering time control in Arabidopsis thaliana; in contrast, methylation of H3K4 correlates with FLC activation. Here we show that loss-of-function of SET DOMAIN GROUP 8 (SDG 8), which encodes a homologue of the yeast SET2 histone methyltransferase, results in reduced dimethylation of histone H3K36, particularly in chromatin associated with the FLC promoter and the first intron, regions that contain essential cis-elements for transcription. sdg8 mutants display reduced FLC expression and flower early, establishing SDG8-mediated H3K36 methylation as a novel epigenetic memory code required for FLC expression in preventing early flowering. This is the first demonstrated role of H3K36 methylation in eukaryote development.

Arabidopsis↗

PubMed2004

Studies on the effects of fpf1 gene on Artemisia annua flowering time and on the linkage between flowering and artemisinin biosynthesis.

The flowering promoting factor1 ( fpf1) from Arabidopsis thaliana was transferred into Artemisia annua L. via Agrobacterium tumefaciens. The fpf1 gene was firstly inserted in the binary vector pBI121 under the control of CaMV 35S promoter to construct the plant expression vector pBIfpf1, then leaf explants of A. annua were infected with A. tumefaciens LBA4404 containing pBIfpf1, and induced shoots. Transgenic plants were obtained through the selection with kanamycin. PCR, PCR-Southern and Southern blot analyses confirmed that the foreign fpf1 gene had been integrated into the A. annua genome. RT-PCR and RT-PCR-Southern analyses suggested that the foreign fpf1 gene had expressed at the transcriptional level. Under short-day conditions, the flowering time of fpf1 transgenic plants was about 20 days earlier than the non-transformed plants; however, no significant differences were detected in artemisinin content between the flowering transgenic plants and the non-flowering non-transgenic plants. These results showed that flowering is not a necessary factor for increasing the artemisinin content, furthermore, there may be no direct linkage between flowering and artemisinin biosynthesis.

Arabidopsis Proteins↗

PubMed2005

CONSTANS activates SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 through FLOWERING LOCUS T to promote flowering in Arabidopsis.

CONSTANS (CO) regulates flowering time by positively regulating expression of two floral integrators, FLOWERING LOCUS T (FT) and SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1), in Arabidopsis (Arabidopsis thaliana). FT and SOC1 have been proposed to act in parallel pathways downstream of CO based on genetic analysis using weak ft alleles, since ft soc1 double mutants showed an additive effect in suppressing the early flowering of CO overexpressor plants. However, this genetic analysis was inconsistent with the sequential induction pattern of FT and SOC1 found in inducible CO overexpressor plants. Hence, to identify genetic interactions of CO, FT, and SOC1, we carried out genetic and expression analyses with a newly isolated T-DNA allele of FT, ft-10. We found that ft-10 almost completely suppressed the early flowering phenotype of CO overexpressor plants, whereas soc1-2 partially suppressed the phenotype, suggesting that FT is the major output of CO. Expression of SOC1 was altered in gain- or loss-of-function mutants of FT, whereas expression of FT remained unchanged in gain- or loss-of-function mutants of SOC1, suggesting that FT positively regulates SOC1 to promote flowering. In addition, inactivation of FT caused down-regulation of SOC1 even in plants overexpressing CO, indicating that FT is required for SOC1 induction by CO. Taken together, these data suggest that CO activates SOC1 through FT to promote flowering in Arabidopsis.

Arabidopsis↗

PubMed2004

A new Arabidopsis gene, FLK, encodes an RNA binding protein with K homology motifs and regulates flowering time via FLOWERING LOCUS C.

Posttranscriptional RNA metabolism plays versatile roles in the regulation of gene expression during eukaryotic growth and development. It is mediated by a group of RNA binding proteins with distinct conserved motifs. In this study, an Arabidopsis (Arabidopsis thaliana) gene, designated FLK, was identified and shown to encode a putative RNA binding protein with K homology motifs. A mutant in which FLK was inactivated by T-DNA insertion exhibited a severe late flowering phenotype both in long and short days. The late flowering phenotype was reversed by gibberellin and vernalization treatments. The FLOWERING LOCUS C (FLC) transcription was greatly upregulated, whereas those of FLOWERING LOCUS T and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 decreased in the mutant. These observations demonstrate that FLK regulates the autonomous flowering pathway via FLC. It is now evident that a battery of different RNA binding proteins are involved in the posttranscriptional regulation of flowering time in Arabidopsis.

Amino Acid Motifs↗

PubMed2005

[The heredity of flower colors and the discovery of flower color chimera in chrysanthemum species].

The reciprocal crosses of yellow colored chrysanthemum x red colored chrysanthemum and white colored chrysanthemum x red colored chrysanthemum were conducted in order to analyze the heredity of flower colors. The results revealed that the heredity of flower colors was very complicated, and mainly exhibited matroclinous characteristics when red colored materials was used as maternal parent but not in the combinations when the yellow or white colored materials were used as maternal parents. The incomplete dominance and mosaic dominance also existed in the heredity of chrysanthemum flower colors. The flower-color chimeras with two kinds of flower buds were discovered in the cross of 3501 x 3509, i.e. one side of the flower buds was completely in red color, which was same as the parental material of 3509, and another side was generally in yellow color with red spots on them. Cytological analysis showed that two sides were both with 36 chromosomes, indicating that the formation of chimera was not resulted from the changes of chromosome numbers, but from the destruction of pigment synthesis genes by the insert of transposable element.

Chimera↗

PubMed2003

Attenuation of FLOWERING LOCUS C activity as a mechanism for the evolution of summer-annual flowering behavior in Arabidopsis.

Plant species have evolved a wide variety of flowering habits, each adapted to maximize reproductive success in their local environment. Even within a species, accessions from different environments can exhibit markedly different flowering behavior. In Arabidopsis, some accessions are rapid-cycling summer annuals, whereas others accessions are late flowering and vernalization responsive and thus behave as winter annuals. Two genes, FLOWERING LOCUS C (FLC) and FRIGIDA (FRI), interact synergistically to confer the winter-annual habit. Previous work has shown that many summer-annual accessions contain null mutations in the FRI gene; thus it appears that these summer-annual accessions have arisen from winter-annual ancestors by losing FRI function. In this work we demonstrate that naturally occurring allelic variation in FLC has provided another route to the evolution of summer-annual flowering behavior in Arabidopsis. We have identified two summer-annual accessions, Da (1)-12 and Shakhdara, that contain functional alleles of FRI, but are early flowering because of weak alleles of FLC. We have also determined that the weak allele of FLC found in Landsberg erecta is naturally occurring. Unlike accessions that have arisen because of loss-of-function mutations in FRI, the FLC alleles from Da (1)-12, Shakhdara, and Landsberg erecta are not nulls; however, they exhibit lower steady-state mRNA levels than strong alleles of FLC. Sequence analysis indicates that these weak alleles of FLC have arisen independently at least twice during the course of evolution.

Alleles↗

PubMed2004

It's time to flower: the genetic control of flowering time.

In plants, successful sexual reproduction and the ensuing development of seeds and fruits depend on flowering at the right time. This involves coordinating flowering with the appropriate season and with the developmental history of the plant. Genetic and molecular analysis in the small cruciform weed, Arabidopsis, has revealed distinct but linked pathways that are responsible for detecting the major seasonal cues of day length and cold temperature, as well as other local environmental and internal signals. The balance of signals from these pathways is integrated by a common set of genes to determine when flowering occurs. Excitingly, it has been discovered that many of these same genes regulate flowering in other plants, such as rice. This review focuses on recent advances in how three of the signalling pathways (the day-length, vernalisation and autonomous pathways) function to control flowering.

Arabidopsis↗