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At least 145 records · Page 8Linked to original sources
PubMed2000

LKP1 (LOV kelch protein 1): a factor involved in the regulation of flowering time in arabidopsis.

In plants, light is not only an energy source but also a very important signal that modulates development and differentiation. Here, we report a putative photo-regulatory factor sequence in LKP1 (LOV kelch protein 1). LKP1 cDNA encodes a protein of 610 amino acids and with a molecular weight of 65 905 with an LOV domain and kelch repeats. LOV domains are present in a number of sensor proteins involved in the detection of light, oxygen or voltage. The LKP1 LOV is very similar to the LOV domains in NPH1, a plasma membrane-associated blue light receptor kinase that regulates phototropism (Huala, E., Oeller, P.W., Liscum, E., Han, I-S., Larsen, E. & Briggs, W.R. (1997) Science, 278, 2120-2123). LKP1 mRNA accumulates in roots, stems, flowers and siliques. It is most abundant in leaves, and least abundant in seeds. Transgenic plants with a beta-glucuronidase (GUS) reporter gene driven by a 1.5 kb LKP1 promoter display strong GUS activity in leaves. Transgenic plants with a 35S:LKP1 cDNA gene overexpress LKP1 mRNA. These plants have elongated hypocotyls and petioles with elongated cells, and exhibit distinct cotyledon movement during the day. Expression of 35S:LKP1 in transgenic Arabidopsis promotes late flowering in plants grown under long-day, but not under short-day conditions. Vernalization does not affect the late flowering phenotype of the 35S:LKP1 plants. Transgenic plants possessing the 35S:GFP-LKP1 construct also have long hypocotyles and petioles, and a late flowering phenotype, suggesting that the GFP-LKP1 fusion protein is active. The GFP-associated fluorescence in 35S:GFP-LKP1 plants is observed in nuclei and cytosol, indicating that LKP1 is a new nucleo-cytoplasmic factor that influences flowering time in the long day pathway of Arabidopsis.

Amino Acid Sequence↗
PubMed2003

Comparative genetic studies on the APRR5 and APRR7 genes belonging to the APRR1/TOC1 quintet implicated in circadian rhythm, control of flowering time, and early photomorphogenesis.

In Arabidopsis thaliana, a number of circadian-associated factors have been identified. Among those, TOC1 (TIMING OF CAB EXPRESSION 1) is believed to be a component of the central oscillator. TOC1 is a member of a small family of proteins, designated as Arabidopsis PSEUDO-RESPONSE REGULATORS (APRR1/TOC1, APRR3, APRR5, APRR7, and APRR9). Nonetheless, it is not very clear whether or not the APRR family members other than APRR1/TOC1 are also implicated in the mechanisms underlying the circadian rhythm. To address this issue further, here we characterized a set of T-DNA insertion mutants, each of which is assumed to have a severe lesion in each one of the quintet genes (i.e. APRR5 and APRR7). For each of these mutants (aprr5-11 and aprr7-11) we demonstrate that a given mutation singly, if not directly, affects the circadian-associated biological events simultaneously: (i) flowering time in the long-day photoperiod conditions, (ii) red light sensitivity of seedlings during the early photomorphogenesis, and (iii) the period of free-running rhythms of certain clock-controlled genes including CCA1 and APRR1/TOC1 in constant white light. These results suggest that, although the quintet members other than APRR1/TOC1 may not be directly integrated into the framework of the central oscillator, they are crucial for a better understanding of the molecular mechanisms underlying the Arabidopsis circadian clock.

Arabidopsis↗
PubMed2002

AtSWI3B, an Arabidopsis homolog of SWI3, a core subunit of yeast Swi/Snf chromatin remodeling complex, interacts with FCA, a regulator of flowering time.

ATP-dependent nucleosome remodeling plays a central role in the regulation of access to chromatin DNA. Swi/Snf remodeling complexes characterized in yeast, Drosophila and mammals all contain a conserved set of core subunits composed of homologs of yeast SNF2-type DNA-dependent ATPase, SNF5 and SWI3 proteins. So far, no complete Swi/Snf-type complex has been characterized in plants. Arabidopsis contains a single SNF5-type gene, BSH, which has been shown to complement the yeast snf5 mutation. Here we describe the characterization of AtSWI3B, the smallest of the four Arabidopsis homologs of SWI3. The gene encoding AtSWI3B is expressed ubiquitously in the plant. AtSWI3B is localized to nuclei and is associated mostly with the chromatin and soluble protein fractions. When expressed in Saccharomyces cerevisiae, the cDNA encoding AtSWI3B partially complements the swi3 mutant phenotype. However, like BSH, AtSWI3B is unable to activate transcription in yeast when tethered to DNA. The analysis by yeast two-hybrid indicates that AtSWI3B is capable of forming homodimers and interacts with BSH as well as with two other members of the Arabidopsis SWI3 family: AtSWI3A and AtSWI3C. The results of phage display screen using recombinant protein, confirmed by direct yeast two-hybrid analyses, indicate that AtSWI3B interacts with FCA, a regulator of flowering time in Arabidopsis. This interaction is through the C-terminal region of FCA, located outside the conserved RNA- and protein-binding domains of this protein.

Amino Acid Sequence↗
PubMed2003

Reciprocal control of flowering time by OsSOC1 in transgenic Arabidopsis and by FLC in transgenic rice.

In a screen for MADS box genes which activate and/or repress flowering in rice, we identified a gene encoding a MADS domain protein (OsSOC1) related to the Arabidopsis gene AtSOC1. AtSOC1 and OsSOC1 show a 97% amino acid similarity in their MADS domain. The rice gene contains a large first intron of 27.6 kb compared to the 1 kb intron in Arabidopsis. OsSOC1 is located on top of the short arm of chromosome 3, tightly linked to the heading date locus, Hd9. OsSOC1 is expressed in vegetative tissues, and expression is elevated at the time of floral initiation, 40-50 days after sowing, and remains uniformly high thereafter, similar to the expression pattern of AtSOC1. The constitutive expression of OsSOC1 in Arabidopsis results in early flowering, suggesting that the rice gene is a functional equivalent of AtSOC1. We were not able to identify FLC-like sequences in the rice genome; however, we show that ectopic expression of the Arabidopsis FLC delays flowering in rice, and the up-regulation of OsSOC1 at the onset of flowering initiation is delayed in the AtFLC transgenic lines. The reciprocal recognition and flowering time effects of genes introduced into either Arabidopsis or rice suggest that some components of the flowering pathways may be shared. This points to a potential application in the manipulation of flowering time in cereals using well characterized Arabidopsis genes.

Journal Article↗
PubMed2006

Comparison of environmental and mutational variation in flowering time in Arabidopsis.

Developmental dynamics can be influenced by external and endogenous factors in a more or less analogous manner. To compare the phenotypic effects of (i) environmental [i.e. standard (stPhP) and extended (exPhP) photoperiods] changes in Arabidopsis wild types and (ii) endogenous genetic variation in eav1-eav61 early flowering mutants, two temporal indicators were analysed, the time to bolting (DtB) and the number of leaves (TLN). It was found that DtB and TLN are differentially affected in different environmental and genetic contexts, and some factors of dynamic convergence were identified. The quantitative response to photoperiod is markedly contingent on the phototrophic input for DtB, but less so for TLN. To discriminate the light quantity and period components in DtB, two novel temporal indicators were determined, LtB (photosynthetic time to bolting) and PChron (DtB h(-1) of photoperiod), respectively. The use of PChron results in a coincidence of the variation profiles across stPhP and exPhP, interpreted as a buffering of the trophic response. Unlike natural accessions and later flowering mutants, the variation profiles across stPhP and eav mutants are significantly divergent, pointing to differences in environmental and genetic variation in flowering time. Yet, phenocopy effects and dynamic convergence between wild-type and mutant profiles are detected by using exPhP and the LtB indicator. Additional analyses of the cauline leaf number (CLN) show that the apical and basal boundaries of the primary inflorescence vary co-ordinately. The finding that the correlativity between CLN and TLN changes across photoperiods suggests that different states of intra-connectedness are involved in ontogenetic specification of flowering time and embodied in the primary inflorescence.

Arabidopsis↗
PubMed2002

Rapid changes in flowering time in British plants.

The average first flowering date of 385 British plant species has advanced by 4.5 days during the past decade compared with the previous four decades: 16% of species flowered significantly earlier in the 1990s than previously, with an average advancement of 15 days in a decade. Ten species (3%) flowered significantly later in the 1990s than previously. These data reveal the strongest biological signal yet of climatic change. Flowering is especially sensitive to the temperature in the previous month, and spring-flowering species are most responsive. However, large interspecific differences in this response will affect both the structure of plant communities and gene flow between species as climate warms. Annuals are more likely to flower early than congeneric perennials, and insect-pollinated species more than wind-pollinated ones.

Climate↗
PubMed2006

Epistatic interactions of three loci regulate flowering time under short and long daylengths in a backcross population of rice.

The short-day plant rice varies greatly in photoperiod sensitivity (PS) for flowering. The hybrid F(1) from a cross between the day-neutral pure line EM93-1 and the weedy rice accession SS18-2 had stronger PS than SS18-2. Some BC(1) (EM93-1/F(1)) segregates were even more sensitive to photoperiod than the F(1), as indicated by later flowering or no flowering after 250 days under a 14-h long daylength. A genome-wide scan identified the quantitative trait loci Se (7.1), Se (7.2) and Se (8) for PS from the BC(1) population, with all alleles that inhibit flowering derived from SS18-2. These three loci regulate the time of flowering under long daylength through their main effects, and di- and trigenic epistases. Under a 10-h short daylength, the regulation is through Se (7.1) and Se (8) main effects and digenic epistases involving all three loci. The short daylength not only nullified the main effect of Se (7.2), but also changed its epistatic effects from inhibiting flowering under long daylength to promoting flowering. The epistases indicate that genes underlying the three PS loci work in the same pathway for the control of flowering. Many non-flowered BC(1)s were the trigenic heterozygote; this suggests that the three PS loci are also involved in genetic control of critical daylength.

Analysis of Variance↗
PubMed2005

Vernalization and flowering time.

Vernalization is the process by which flowering is promoted by prolonged exposure to the cold of a typical winter. In certain plant species, the role of vernalization is to suppress the expression of genes that encode repressors of flowering. In Arabidopsis, this suppression is an epigenetic phenomenon in the sense that it is mitotically stable in the spring after the inducing signal, cold, is no longer perceived. This epigenetic silencing results from the modification of the chromatin of flowering repressors.

Arabidopsis↗
PubMed2000

Characterization of a gene from Zea mays related to the Arabidopsis flowering-time gene LUMINIDEPENDENS.

The molecular biology of flowering has been most extensively studied in the quantitative long-day plant Arabidopsis thaliana. The Arabidopsis LUMINIDEPENDENS (LD) gene encodes a potential transcriptional regulator that acts as a positive effector of flowering, at least in part through suppression of the floral inhibitor gene FLC. As an initial step to explore the conservation of the molecular mechanisms of flowering among plants of various flowering habits, and to further investigate the molecular action(s) of LD, we have identified a gene from maize (Zea mays) that is closely related to Arabidopsis LD. The major product of this gene, which we have designated ZmLD for Zea mays LUMINIDEPENDENS, contains four conserved regions that may constitute functionally important components of the LD proteins. One of these regions closely resembles the canonical homeodomain. The ZmLD gene exists as a single copy in the maize genome, and generates a major ca. 4.0 kb transcript, and a minor ca. 2.6 kb transcript that results from alternative transcriptional termination. The 4.0 kb ZmLD alpha transcript accumulated to highest levels in proliferative tissues, including the shoot apex and developing inflorescences. Expression of ZnLD alpha under control of the Arabidopsis LD promoter in transgenic Arabidopsis caused developmental defects similar to those conferred by loss-of-function mutations in a class of genes involved in maintaining the proliferative nature of the shoot, inflorescence, and floral meristems. These effects were not influenced markedly by the activities of the Arabidopsis LD or FLC genes. We consider the implications for the conservation of LD function between maize and Arabidopsis.

Amino Acid Sequence↗
PubMedDate not supplied

Analysis of flowering time in ecotypes of Arabidopsis thaliana.

There exists variation in the timing of the initiation of flowering among different ecotypes of Arabidopsis thaliana. We have examined the basis of this variation between the early flowering Columbia (Col) ecotype and the late flowering ecotypes. Coimbra (Co-4), Geneva (Ge-2), and Zu-rich (Zu-0). In crosses of Col to Co-4, Ge-2, and Zu-0, the late flowering trait behaved as a single dominant gene the F1 plants were late flowering and in segregating F, populations a 3:1 ratio of late to early flowering plants was observed. This dominant gene resides in a region of chromosome 4 that contains a gene (FRIGIDA) conferring late flowering in certain other Arabidopsis ecotypes. Allelism tests indicate that the same genesis responsible for late flowering in Co-4, Ge-2. Zu-0, and the San Feliu (Sf-2) ecotype. These and previous results indicate that FRIGIDA accounts for much of the later flowering observed in various ecotypes of Arabidopsis.

Arabidopsis↗
PubMed1998

Control of flowering time.

The multiple promotive and repressive pathways controlling flowering have been further defined by analysis of genetic interactions and the activation of floral meristem identity genes. Cloning of additional genes in these pathways has uncovered some of the molecular processes that control the timing of the transition to reproductive development.

Arabidopsis↗
PubMed2002

A phytochrome-associated protein phosphatase 2A modulates light signals in flowering time control in Arabidopsis.

Reversible protein phosphorylation, which is catalyzed by functionally coupled protein kinases and protein phosphatases, is a major signaling mechanism in eukaryotic cellular functions. The red and far-red light-absorbing phytochrome photoreceptors are light-regulated Ser/Thr-specific protein kinases that regulate diverse photomorphogenic processes in plants. Here, we demonstrate that the phytochromes functionally interact with the catalytic subunit of a Ser/Thr-specific protein phosphatase 2A designated FyPP. The interactions were influenced by phosphorylation status and spectral conformation of the phytochromes. Recombinant FyPP efficiently dephosphorylated oat phytochrome A in the presence of Fe(2+) or Zn(2+) in a spectral form-dependent manner. FyPP was expressed predominantly in floral organs. Transgenic Arabidopsis plants with overexpressed or suppressed FyPP levels exhibited delayed or accelerated flowering, respectively, indicating that FyPP modulates phytochrome-mediated light signals in the timing of flowering. Accordingly, expression patterns of the clock genes in the long-day flowering pathway were altered greatly. These results indicate that a self-regulatory phytochrome kinase-phosphatase coupling is a key signaling component in the photoperiodic control of flowering.

Amino Acid Sequence↗
PubMed2004

Regulation of flowering time by FVE, a retinoblastoma-associated protein.

The initiation of flowering in plants is controlled by environmental and endogenous signals. Molecular analysis of this process in Arabidopsis thaliana indicates that environmental control is exerted through the photoperiod and vernalization pathways, whereas endogenous signals regulate the autonomous and gibberellin pathways. The vernalization and autonomous pathways converge on the negative regulation of FLC, a gene encoding a MADS-box protein that inhibits flowering. We cloned FVE, a component of the autonomous pathway that encodes AtMSI4, a putative retinoblastoma-associated protein. FVE interacted with retinoblastoma protein in immunoprecipitation assays, and FLC chromatin was enriched in acetylated histones in fve mutants. We conclude that FVE participates in a protein complex repressing FLC transcription through a histone deacetylation mechanism. Our data provide genetic evidence of a new developmental function of these conserved proteins and identify a new genetic mechanism in the regulation of flowering.

Arabidopsis↗
PubMed1993

Chromosome walking with YAC clones in Arabidopsis: isolation of 1700 kb of contiguous DNA on chromosome 5, including a 300 kb region containing the flowering-time gene CO.

The co mutation of Arabidopsis thaliana causes a late-flowering phenotype that is insensitive to day-length. The mutation was mapped previously to the upper arm of chromosome 5, approximately 1.6 cM from the chalcone synthase gene (CHS). We were provided with five yeast artificial chromosome (YAC) libraries and used these to perform a chromosome walk from CHS to the CO gene. In this paper we report the isolation of 1700 kb of contiguous Arabidopsis DNA, which represents approximately 1%-2% of the genome, inserted in YACs. This required the detailed analysis of 67 YACs, from which 87 end probes were isolated and examined in hybridisation experiments. This analysis showed that approximately 40% of the YACs presented problems in chromosome walking experiments because they contained repetitive sequence at one of their termini, were chimaeric or because part of the plant DNA was deleted. DNA fragments isolated from YACs were used as restriction fragment length polymorphism (RFLP) markers to localize CO to a 300 kb region within the cloned DNA. We compare the physical distance between CHS and CO with the genetic distance and find that in this region 1 cM is equivalent to approximately 200 kb.

Arabidopsis↗
PubMed1999

FLD interacts with CO to affect both flowering time and floral initiation in Arabidopsis thaliana.

fld and co, both with significantly delayed flowering, are characterized as late-flowering mutations in Arabidopsis thaliana. Double mutants between fld-2 and co-3 were generated and the phenotypes characterized. Double mutants flower later than both single mutant parents, suggesting that there is an additive effect. In addition, the formation of flowers in double mutants was altered and showed a novel phenotype. Double mutant flowers contained a much longer stalk (pedicel). Sepals and petals were absent. Several leaf-like structures were produced in the position normally occupied by sepals and the organ numbers were reduced. The carpels were morphologically normal. The stamens produced were usually aborted in the early stage, thus, the flowers were sterile. The additive phenotype observed in double mutants provides evidence to support that these two genes, FLD and CO, are not only involved in rosette-to-inflorescence transition but also involved in the flower formation. This result also indicates that FLD and CO promote the reproductive program through two different pathways.

Arabidopsis↗
PubMed2003

Regulation of flowering time by histone acetylation in Arabidopsis.

The Arabidopsis autonomous floral-promotion pathway promotes flowering independently of the photoperiod and vernalization pathways by repressing FLOWERING LOCUS C (FLC), a MADS-box transcription factor that blocks the transition from vegetative to reproductive development. Here, we report that FLOWERING LOCUS D (FLD), one of six genes in the autonomous pathway, encodes a plant homolog of a protein found in histone deacetylase complexes in mammals. Lesions in FLD result in hyperacetylation of histones in FLC chromatin, up-regulation of FLC expression, and extremely delayed flowering. Thus, the autonomous pathway regulates flowering in part by histone deacetylation. However, not all autonomous-pathway mutants exhibit FLC hyperacetylation, indicating that multiple means exist by which this pathway represses FLC expression.

Acetylation↗