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PubMed2002

The ELF4 gene controls circadian rhythms and flowering time in Arabidopsis thaliana.

Many plants use day length as an environmental cue to ensure proper timing of the switch from vegetative to reproductive growth. Day-length sensing involves an interaction between the relative length of day and night, and endogenous rhythms that are controlled by the plant circadian clock. Thus, plants with defects in circadian regulation cannot properly regulate the timing of the floral transition. Here we describe the gene EARLY FLOWERING 4 (ELF4), which is involved in photoperiod perception and circadian regulation. ELF4 promotes clock accuracy and is required for sustained rhythms in the absence of daily light/dark cycles. elf4 mutants show attenuated expression of CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), a gene that is thought to function as a central oscillator component. In addition, elf4 plants transiently show output rhythms with highly variable period lengths before becoming arrhythmic. Mutations in elf4 result in early flowering in non-inductive photoperiods, which is probably caused by elevated amounts of CONSTANS (CO), a gene that promotes floral induction.

Arabidopsis↗
PubMed2003

Characterization and functional analysis of three wheat genes with homology to the CONSTANS flowering time gene in transgenic rice.

The CONSTANS (CO) gene of Arabidopsis plays a key role in the photoperiodic flowering pathway. To investigate photoperiod responses in cereals in more detail, we isolated three kinds of CO/Hd1 (rice ortholog of CO) homolog from hexaploid wheat, derived from the A, B, and D genomes and designated as wheat ortholog of CO from A genome (TaHd1-1), TaHd1-2, and TaHd1-3, respectively. They were highly similar to each other and to Hd1, and in addition harbored two conserved regions: two zinc finger motifs and CONSTANS, CONSTANS-LIKE and TIMING OF CAB EXPRESSION 1 (CCT) domain like CO/Hd1. They were located on the long arm of the homoeologous chromosome 6. TaHd1-2 harbored a 63-bp deletion at the promoter region containing the GATA-1 box, and consequently, we detected no subsequent transcript. The TaHd1-1 genomic clone was introduced to a rice line deficient in Hd1 function. Transgenic plants complemented the functions of rice Hd1: they promoted heading under short-day (SD) conditions and delayed it under long-day (LD)/natural conditions, indicating that Hd1 proteins from SD and LD plants share common structures and functions.

Amino Acid Sequence↗
PubMed1998

Analysis of natural allelic variation at flowering time loci in the Landsberg erecta and Cape Verde Islands ecotypes of Arabidopsis thaliana.

We have analyzed the flowering behavior of two Arabidopsis ecotypes: the laboratory strain Landsberg erecta (Ler) and an ecotype from the tropical Cape Verde Islands (Cvi). They differ little in their flowering phenotypes and in their responses to photoperiod length changes and to vernalization treatment. However, segregating populations derived from crosses between them showed a much larger variation. An approach of quantitative trait locus (QTL) mapping in recombinant inbred lines (RILs) grown under three environments differing in day-length and/or vernalization treatment has been used to detect and locate flowering loci. Four main QTLs were identified, designated early day-length insensitive (EDI), flowering F, G, and H (FLF, FLG, and FLH, respectively), to which most of the flowering behavior differences could be attributed. To further characterize the individual loci, near isogenic lines were constructed by introgressing Cvi early alleles of EDI and FLH into the Ler genetic background. EDI-Cvi alleles produce earliness under both long- and short-day photoperiods, rendering Ler plants almost day-length neutral. In addition, RILs were selected to analyze FLF and FLG. These loci interact epistatically and RILs carrying late alleles at FLF and FLG were very responsive to vernalization and showed an increased response to photoperiod length changes. The possible role of these loci for the control of flowering is discussed in the context of the current Arabidopsis model.

Alleles↗
PubMed2004

Functional analyses of the flowering time gene OsMADS50, the putative SUPPRESSOR OF OVEREXPRESSION OF CO 1/AGAMOUS-LIKE 20 (SOC1/AGL20) ortholog in rice.

A late-flowering mutant was isolated from rice T-DNA-tagging lines. T-DNA had been integrated into the K-box region of Oryza sativa MADS50 (OsMADS50), which shares 50.6% amino acid identity with the Arabidopsis MADS-box gene SUPPRESSOR OF OVEREXPRESSION OF CO 1/AGAMOUS-LIKE 20 (SOC1/AGL20). While overexpression of OsMADS50 caused extremely early flowering at the callus stage, OsMADS50 RNAi plants exhibited phenotypes of late flowering and an increase in the number of elongated internodes. This confirmed that the phenotypes observed in the knockout (KO) plants are because of the mutation in OsMADS50. RT-PCR analyses of the OsMADS50 KO and ubiquitin (ubi):OsMADS50 plants showed that OsMADS50 is an upstream regulator of OsMADS1, OsMADS14, OsMADS15, OsMADS18, and Hd (Heading date)3a, but works either parallel with or downstream of Hd1 and O. sativa GIGANTEA (OsGI). These results suggest that OsMADS50 is an important flowering activator that controls various floral regulators in rice.

Base Sequence↗
PubMed2005

Looking into flowering time in almond (Prunus dulcis (Mill) D. A. Webb): the candidate gene approach.

Blooming time is one of the most important agronomic traits in almond. Biochemical and molecular events underlying flowering regulation must be understood before methods to stimulate late flowering can be developed. Attempts to elucidate the genetic control of this process have led to the identification of a major gene (Lb) and quantitative trait loci (QTLs) linked to observed phenotypic differences, but although this gene and these QTLs have been placed on the Prunus reference genetic map, their sequences and specific functions remain unknown. The aim of our investigation was to associate these loci with known genes using a candidate gene approach. Two almond cDNAs and eight Prunus expressed sequence tags were selected as candidate genes (CGs) since their sequences were highly identical to those of flowering regulatory genes characterized in other species. The CGs were amplified from both parental lines of the mapping population using specific primers. Sequence comparison revealed DNA polymorphisms between the parental lines, mainly of the single nucleotide type. Polymorphisms were used to develop co-dominant cleaved amplified polymorphic sequence markers or length polymorphisms based on insertion/deletion events for mapping the candidate genes on the Prunus reference map. Ten candidate genes were assigned to six linkage groups in the Prunus genome. The positions of two of these were compatible with the regions where two QTLs for blooming time were detected. One additional candidate was localized close to the position of the Evergrowing gene, which determines a non-deciduous behaviour in peach.

Chromosome Mapping↗
PubMed1999

Ectopic expression of tobacco MADS genes modulates flowering time and plant architecture.

MADS genes encode regulatory factors that are involved in various developmental steps of the plant life cycle. During flower development, they regulate the early step of specifying floral meristem identity as well as the later step of determining the fate of floral organ primordia. Here, we report the isolation of two cDNA clones, NsMADS2 and NsMADS3, from a long-day tobacco species, Nicotiana sylvestris, which encode MADS domain-containing proteins. The NsMADS2 amino acid sequence showed 66% identity to SQUA and 64% to AP1. NsMADS3 showed a high degree of amino acid identity with FBP2 (98%), DEFH 72 (89%), DEFH 200 (88%), and AGL9 (76%). RNA blot analyses of NsMADS2 and NsMADS3 revealed that both transcripts were present in floral organs, but not in vegetative organs such as the leaf, root, stem, and 10 d old seedlings. The NsMADS2 transcript was localized in all four whorls and the NsMADS3 transcript was restricted in the three inner whorls of floral organs. The ectopic expression of NsMADS2 using the CaMV 35S promoter caused early flowering and lengthened internode length in transgenic tobacco plants. The ectopic expression of NsMADS3 also caused early flowering phenotype in transgenic tobacco plants, but the plants exhibited reduced apical dominance. Possible implications of these results in relation to the functions of NsMADS2 and NsMADS3 are discussed.

Amino Acid Sequence↗
PubMed2004

The maize ID1 flowering time regulator is a zinc finger protein with novel DNA binding properties.

The INDETERMINATE protein, ID1, plays a key role in regulating the transition to flowering in maize. ID1 is the founding member of a plant-specific zinc finger protein family that is defined by a highly conserved amino sequence called the ID domain. The ID domain includes a cluster of three different types of zinc fingers separated from a fourth C2H2 finger by a long spacer; ID1 is distinct from other ID domain proteins by having a much longer spacer. In vitro DNA selection and amplification binding assays and DNA binding experiments showed that ID1 binds selectively to an 11 bp consensus motif via the ID domain. Unexpectedly, site-directed mutagenesis of the ID1 protein showed that zinc fingers located at each end of the ID domain are not required for binding to the consensus motif despite the fact that one of these zinc fingers is a canonical C2H2 DNA binding domain. In addition, an ID1 in vitro deletion mutant that lacks the extra spacer between zinc fingers binds the same 11 bp motif as normal ID1, suggesting that all ID domain-containing proteins recognize the same DNA target sequence. Our results demonstrate that maize ID1 and ID domain proteins have novel zinc finger configurations with unique DNA binding properties.

Base Sequence↗
PubMed2003

A nuclear protease required for flowering-time regulation in Arabidopsis reduces the abundance of SMALL UBIQUITIN-RELATED MODIFIER conjugates.

The Arabidopsis mutant early in short days4 (esd4) shows extreme early flowering and alterations in shoot development. We have identified ESD4 and demonstrate that it encodes a nuclear protein located predominantly at the periphery of the nucleus. ESD4 contains a segment of >200 amino acids with strong similarity to yeast and animal proteases that are specific for the protein modifier SMALL UBIQUITIN-RELATED MODIFIER (SUMO). ESD4 shows a similar function to these proteases in vitro and processes the precursor of Arabidopsis SUMO (AtSUMO) to generate the mature form. This activity of ESD4 is prevented by mutations that affect the predicted active site of the protease or the cleavage site of the AtSUMO precursor. In yeast, these proteases also recycle SUMO from conjugates, and this appears to be the major role of ESD4 in vivo. This is suggested because esd4 mutants contain less free AtSUMO and more SUMO conjugates than wild-type plants, and a transgene expressing mature SUMO at high levels enhanced aspects of the esd4 phenotype. ESD4 defines an important role for protein modification by AtSUMO in the regulation of flowering.

Amino Acid Sequence↗
PubMed2002

Multiple roles of Arabidopsis VRN1 in vernalization and flowering time control.

Arabidopsis VRN genes mediate vernalization, the process by which a long period of cold induces a mitotically stable state that leads to accelerated flowering during later development. VRN1 encodes a protein that binds DNA in vitro in a non-sequence-specific manner and functions in stable repression of the major target of the vernalization pathway, the floral repressor FLC. Overexpression of VRN1 reveals a vernalization-independent function for VRN1, mediated predominantly through the floral pathway integrator FT, and demonstrates that VRN1 requires vernalization-specific factors to target FLC.

Amino Acid Sequence↗
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↗
PubMed2006

The maize INDETERMINATE1 flowering time regulator defines a highly conserved zinc finger protein family in higher plants.

BACKGROUND: The maize INDETERMINATE1 gene, ID1, is a key regulator of the transition to flowering and the founding member of a transcription factor gene family that encodes a protein with a distinct arrangement of zinc finger motifs. The zinc fingers and surrounding sequence make up the signature ID domain (IDD), which appears to be found in all higher plant genomes. The presence of zinc finger domains and previous biochemical studies showing that ID1 binds to DNA suggests that members of this gene family are involved in transcriptional regulation. RESULTS: Comparison of IDD genes identified in Arabidopsis and rice genomes, and all IDD genes discovered in maize EST and genomic databases, suggest that ID1 is a unique member of this gene family. High levels of sequence similarity amongst all IDD genes from maize, rice and Arabidopsis suggest that they are derived from a common ancestor. Several unique features of ID1 suggest that it is a divergent member of the maize IDD family. Although no clear ID1 ortholog was identified in the Arabidopsis genome, highly similar genes that encode proteins with identity extending beyond the ID domain were isolated from rice and sorghum. Phylogenetic comparisons show that these putative orthologs, along with maize ID1, form a group separate from other IDD genes. In contrast to ID1 mRNA, which is detected exclusively in immature leaves, several maize IDD genes showed a broad range of expression in various tissues. Further, Western analysis with an antibody that cross-reacts with ID1 protein and potential orthologs from rice and sorghum shows that all three proteins are detected in immature leaves only. CONCLUSION: Comparative genomic analysis shows that the IDD zinc finger family is highly conserved among both monocots and dicots. The leaf-specific ID1 expression pattern distinguishes it from other maize IDD genes examined. A similar leaf-specific localization pattern was observed for the putative ID1 protein orthologs from rice and sorghum. These similarities between ID1 and closely related genes in other grasses point to possible similarities in function.

Amino Acid Sequence↗
PubMed2026

Human m6A demethylase FTO modulates the flowering time of tomato plants under low-temperature stress.

N6-methyladenosine (m6A) RNA modification plays an important role in plant development and environmental stress responses. However, whether m6A demethylation modulates flowering under low-temperature (LT) stress in tomatoes remains unclear. Here, we investigated whether ectopic expression of FTO, a well-characterized human m6A demethylase, influences flowering and post-transcriptional behaviour in tomato (Solanum lycopersicum) under LT conditions. Flowering of transgenic tomato plants expressing FTO was analyzed under LT and normal conditions (NC), and the impacts of FTO on transcripts-specific m6A level, mRNA stability and splicing efficiency of flowering-related genes were evaluated using RT-qPCR, LC-MS/MS, m6A-IP-qPCR, and RNA decay and splicing analyses. FTO-expressing plants exhibited accelerated flowering specifically under LT, whereas no significant differences were observed under normal growth conditions. This phenotype was accompanied by increased expression of positive floral regulators (SlMC, SlFCA, and SlJ2) and decreased expression of negative regulators (SlSVP, SlSP, and SlTMF) under LT conditions. Notably, these expression changes were associated with altered mRNA stability, with positive regulators showing increased stability and negative regulators showing reduced stability under LT conditions. m6A-IP-qPCR analysis indicated reduced m6A enrichment in these selected transcripts in FTO-expressing plants. In addition to effects on mRNA stability, FTO expression was associated with changes in the splicing efficiency of SlMC transcripts. Collectively, our findings indicate that human FTO functions as an mRNA m6A demethylase in tomatoes and is associated with altered RNA regulatory processes under LT conditions. These findings suggest that m6A-mediated post-transcriptional regulation contributes to stress-induced flowering plasticity under LT conditions, rather than direct activation of canonical flowering pathways.

Abiotic stress↗
PubMed2005

Role of chromatin modification in flowering-time control.

The regulation of the FLC locus provides a plant model of how chromatin-modifying systems have emerged as important components in the control of a major developmental switch, the transition to flowering. Genetic and molecular studies have revealed that three systems of FLC regulation (vernalization, FRI and the autonomous pathway) all influence the state of FLC chromatin. Histone H3 trimethylation at lysine 4 and histone acetylation are associated with active FLC expression, whereas histone deacetylation and histone H3 dimethylation at lysines 9 and 27 are involved in FLC repression. These chromatin modifications provide an additional level of regulation of gene expression beyond that of the transcription factors that recruit RNA polymerase to target genes.

Arabidopsis↗
PubMed1999

The Arabidopsis flowering-time gene LUMINIDEPENDENS is expressed primarily in regions of cell proliferation and encodes a nuclear protein that regulates LEAFY expression.

Mutations in the LUMINIDEPENDENS (LD) gene of Arabidopsis thaliana (L.) Heynh. (Arabidopsis) confer a late-flowering phenotype, indicating that LD normally functions to promote the floral transition. RNA and protein blot analyses, along with the analysis of transgenic plants containing a fusion between a genomic fragment of LD and the reporter gene uidA (GUS), indicate that LD is expressed primarily ipical proliferative regions of the shoot and root, including the shoot apical meristem and leaf primordia. Subcellular localization studies indicate that LD is a nuclear protein, consistent with its previously proposed transcriptional regulatory role. We have also found that in an apetala1 cauliflower (ap1 cal) background the ld mutation converts the reproductive shoot apex to a more vegetative state, a phenotype that is similar to that seen for the leafy (lfy) mutant. Furthermore, in situ hybridization analysis indicates that LFY levels are drastically reduced at the apex of ld ap1 cal plants after bolting. These data are consistent with the idea that at least one function of LD is to participate in the regulation of LFY.

Arabidopsis↗
PubMed2006

Role of plant CBP/p300-like genes in the regulation of flowering time.

CREB-binding protein (CBP) and its homolog p300 possess histone acetyltransferase activity and function as key transcriptional co-activators in the regulation of gene expression that controls differentiation and development in animals. However, the role of CBP/p300-like genes in plants has not yet been elucidated. Here, we show that Arabidopsis CBP/p300-like genes promote flowering by affecting the expression of a major floral repressor FLOWERING LOCUS C (FLC). Although animal CBP and p300 generally function as co-activators, Arabidopsis CBP/p300-like proteins are required for the negative regulation of FLC. This CBP/p300-mediated FLC repression may involve reversible protein acetylation independent of histone modification within FLC chromatin.

Arabidopsis↗
PubMedDate not supplied

A major gene for time of flowering in chickpea.

A major gene for the number of days from sowing to appearance of the first flower (time of flowering) was identified in a cross between an extrashort duration chickpea (Cicer arietinum L.) variety, ICCV 2, and a medium duration variety, JG 62. The F2 population was advanced through the single-seed-descent method to develop random recombinant inbred lines (RILs). Time of flowering was recorded for the parents and 66 F(6) RILs from this cross that were grown in a Vertisol field in the post-rainy season of 1996-1997. Similarly the parents, F(1) and F(10) RILs were evaluated in 1997-1998. The F(1) flowered along with JG 62. The time of flowering for the two sets of RILs showed bimodal distributions with nearly equal peaks. One peak corresponded with ICCV 2 and the other with JG 62. This suggests that a single gene controls the difference for the time of flowering between ICCV 2 and JG 62 and the allele carried by the latter parent is dominant. To our knowledge no gene has been identified for the time of flowering in chickpea. Therefore the allele carried by JG 62 is designated as Efl-1 and that by ICCV 2 as efl-1. The proposed genotype for ICCV 2 is efl-1 efl-1 and for JG 62 is Efl-1 Efl-1. The genotype efl-1 efl-1 reduces the time of flowering at ICRISAT by nearly 3 weeks. The significance of this gene for breeding for early maturity and genome mapping has been discussed.

Crosses, Genetic↗
PubMed1996

The rosette habit of Arabidopsis thaliana is dependent upon phytochrome action: novel phytochromes control internode elongation and flowering time.

A major function of phytochromes in light-grown plants involves the perception of changes in the relative amounts of red and far-red light (R:FR ratio) and the initiation of the shade-avoidance response. In Arabidopsis thaliana, this response is typified by increased elongation growth of petioles and accelerated flowering and can be fully induced by end-of-day far-red light (EOD FR) treatments. Phytochrome B-deficient (phyB) mutants, which have a constitutive elongated-petiole and early-flowering pheno-type, do not display a petiole elongation growth response to EOD FR, but they do respond to EOD FR by earlier flowering. Seedlings deficient in both phytochrome A and phytochrome B (phyA phyB), have a greatly reduced stature compared with wild-type or either monogenic mutant. The phyA phyB double null mutants also respond to EOD FR treatments by flowering early, suggesting the operation of novel phytochromes. Contrary to the behaviour of wild-type or monogenic phyA or phyB seedlings, petiole elongation in phyA phyB seedlings is reduced in response to EOD FR treatments. This reduction in petiole elongation is accompanied by the appearance of elongated internodes such that under these conditions the plants no longer display a rosette habit.

Arabidopsis↗