Activation Tagging of the Floral Inducer FT (original) (raw)
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Plant Biotechnology, 2009
One of the most important events during the life cycle of a plant is the transition from the vegetative to the reproductive state (Bernier et al. 2000). Appropriate timing so that this occurs during the most favorable conditions is crucial in agriculture and horticulture for maximizing reproductive success (Boss et al. 2004). Moreover, to maximize this reproductive success, it is important for flower structure during fertilization to be as complete and intact as possible so that pollination followed by fertilization occurs under the best conditions. In natural conditions in temperate areas, many predictable and unpredictable factors in the environment influence flowering time (Lang 1965; Bernier et al. 1981; Thomas and Vince-Prue 1997). The highly predictable factors include annual changes in day length, photoperiod, and the period of winter cold or vernalization. The ability to detect seasonal changes and to respond to them also confers a selective advantage to plants because it provides a means of anticipating and consequently preventing the adverse effects of a particular seasonal environment. The photoperiodic control of flowering time is tightly linked to the circadian clock and influences the expression of genes regulating the transition from vegetative to reproductive phase. A genetic approach to investigating the mechanisms required to secure correct timing of the floral transition has mainly been focused on Arabidopsis thaliana. Considering the process of flowering as a default developmental program (Boss et al. 2004; Komeda 2004) that must be suppressed early in the life cycle of the plant, these previous studies divided floral pathways into those that enable the floral transition and those that promote it. Based on their model, the floral enabling pathway would regulate expression of floral repressors. In Arabidopsis, two floral activators, GIGANTEA (GI) and CONSTANS (CO), play key roles in photoperiodic flowering (Fowler et al. 1999; Park et al. 1999), and it has been proposed that GI plays dual roles, namely in regulating period length and circadian phase and in promoting the expression of the circadian clock output pathway that includes CO and FLOWERING LOCUS T (FT) to promote flowering (Mizoguchi et al. 2005). FLOWERING LOCUS C (FLC) and SHORT VEGETATIVE PHASE (SVP) encode MADS-box proteins. Both FLC and SVP negatively regulate the transition, but FLC is considered the more central regulator of the flowering enabling pathway (Michaels and Amasino 1999; Hartmann et al. 2000). In Arabidopsis, two closely related MYB proteins with redundant functions, LATE ELONGATED
The Plant …, 2001
CONSTANS promotes¯owering of Arabidopsis in response to long-day conditions. We show that CONSTANS is a member of an Arabidopsis gene family that comprises 16 other members. The CO-Like proteins encoded by these genes contain two segments of homology: a zinc ®nger containing region near their amino terminus and a CCT (CO, CO-Like, TOC1) domain near their carboxy terminus. Analysis of seven classical co mutant alleles demonstrated that the mutations all occur within either the zinc ®nger region or the CCT domain, con®rming that the two regions of homology are important for CO function. The zinc ®ngers are most similar to those of B-boxes, which act as protein±protein interaction domains in several transcription factors described in animals. Segments of CO protein containing the CCT domain localize GFP to the nucleus, but one mutation that affects the CCT domain delays¯owering without affecting the nuclear localization function, suggesting that this domain has additional functions. All eight co alleles, including one recovered by pollen irradiation in which DNA encoding both B-boxes is deleted, are shown to be semidominant. This dominance appears to be largely due to a reduction in CO dosage in the heterozygous plants. However, some alleles may also actively delay¯owering, because overexpression from the CaMV 35S promoter of the co-3 allele, that has a mutation in the second B-box, delayed¯owering of wild-type plants. The signi®cance of these observations for the role of CO in the control of¯owering time is discussed.
Flowering-time genes modulate the response to LEAFY activity
Genetics, 1998
Among the genes that control the transition to flowering in Arabidopsis is a large group whose inactivation causes a delay in flowering. It has been difficult to establish different pathways in which the flowering-time genes might act, because mutants with lesions in these genes have very similar phenotypes. Among the putative targets of the flowering-time genes is another group of genes, which control the identity of individual meristems. Overexpression of one of the meristem-identity genes, LEAFY, can cause the precocious generation of flowers and thus early flowering. We have exploited the opposite phenotypes seen in late-flowering mutants and LEAFY overexpressers to clarify the genetic interactions between flowering-time genes and LEAFY. According to epistatic relationships, we can define one class of flowering-time genes that affects primarily the response to LEAFY activity, and another class of genes that affects primarily the transcriptional induction of LEAFY. These observat...
Gene, 2016
Here we analyzed in leaves the effect of FT overexpression driven by meristem-specific KNAT1 gene homolog of Arabidopsis thaliana (Lincoln et al., 1994; Long et al., 1996) on the transcriptomic response during plant development. Our results demonstrated that meristematic FT overexpression generates a phenotype with an early flowering independent of photoperiod when compared with wild type (WT) plants. Arabidopsis FToverexpressor lines (AtFTOE) did not show significant differences compared with WT lines neither in leaf number nor in rosette diameter up to day 21, when AtFTOE flowered. After this period AtFTOE plants started flower production and no new rosette leaves were produced. Additionally, WT plants continued on vegetative stage up to day 40, producing 12-14 rosette leaves before flowering. Transcriptomic analysis of rosette leaves studied by sequencing Illumina RNA-seq allowed us to determine the differential expression in mature leaf rosette of 3652 genes, being 626 of them up-regulated and 3026 down-regulated. Overexpressed genes related with flowering showed up-regulated transcription factors such as MADS-box that are known as flowering markers in meristem and which overexpression has been related with meristem identity preservation and the transition from vegetative to floral stage. Genes related with sugar transport have shown a higher demand of monosaccharides derived from the hydrolysis of sucrose to glucose and probably fructose, which can also be influenced by reproductive stage of AtFTOE plants.
A Parade on Molecular Control of Flowering
International Journal of Environment, Agriculture and Biotechnology, 2016
Flower is a reproductive part of plant which contains complex array of functionally specialized structures.Photoperiodism, or the ability of an organism to detect day length, makes it possible for an event to occur at a particular time of year, thus allowing for a seasonal response. Circadian rhythms and photoperiodism have the common property of responding to cycles of light and darkness. Plant physiologists believed that the correlation between long days and flowering was a consequence of the accumulation of photosynthetic products synthesized during long days. Vernalization causes stable changes in the pattern of gene expression in the meristem, gene expression that are still stable even after vernalization is removed. The organ identity genes initially were identified through mutations that dramatically alter the structure and thus the identity of the floral organs produced in two adjacent whorls. The patterns of organ formation in the wild type and most of the mutant phenotypes are predicted and explained by ABC model of flower development. the transition to flowering involves a complex system of interacting factors that include among carbohydrates, gibberellins, cytokinins, bromeliads and ethylene.
Genetic interactions among late-flowering mutants of Arabidopsis, Genetics 148, 885-892
Genetics
Flowering time in Arabidopsis is controlled by a large number of genes, identified by induced mutations. Forty-two double mutants involving 10 of these loci were obtained and analyzed for their flowering behavior under long-day conditions, with and without vernalization, and under short-day conditions. The genetic interactions between the various mutants proved to be complex, although a major epistatic group (called group A) could be identified corresponding to the mutants, which are relatively insensitive to vernalization and daylength. In contrast, the genetic behavior of the mutants much more responsive to these environmental factors (group B) is more complex. The vernalization responsiveness of the group B mutants did not compensate for the lateness of the group A mutants. This indicated that these genes do not control vernalization sensitivity as such, but provide a factor that becomes limiting in short days. The classification of these mutants in different physiological groups is discussed in relation to the detected genetic interactions, and based on these interactions a more detailed model of their role in flowering initiation is proposed.
Different Roles of Flowering-Time Genes in the Activation of Floral Initiation Genes in Arabidopsis
The Plant Cell, 1997
We have analyzed double mutants that combine late-flowering mutations at four flowering-time loci (f E, FPA, F WA, and F T) with mutations at the LEAFY (L N) , APETALA7 (AP7), and TERMlNAL FLOWER7 (TFL7) loci involved in the floral initiation process (FLIP). Double mutants between ft-7 or fwa-7 and lfy-6 completely lack flowerlike structures, indicating that both F WA and F T act redundantly with LF Y to control AP7. Moreover, the phenotypes of ft-7 ap7-7 and fwa-7 ap7-7 double mutants are reminiscent of the phenotype of ap7-7 cal-7 double mutants, suggesting that FWA and F T could also be involved in the control of other FLlP genes. Such extreme phenotypes were not observed in double mutants between f v e d or fpa-7 and lfy-6 or ap7-7. Each of these showed a phenotype similar to that of ap7-7 or lfy-6 mutants grown under noninductive photoperiods, suggesting a redundant interaction with FLlP genes. Finally, the phenotype of double mutants combining the late-flowering mutations with tfH-2 were also consistent with the different roles of flowering-time genes.
Journal of Experimental Botany, 2013
Flowering time in the model plant Arabidopsis thaliana is regulated by both external environmental signals and internal developmental pathways. Natural variation at the FLOWERING H (FLH) locus has previously been described, with alleles present in the Cape Verde Islands accession causing early flowering, particularly after vernalization. The mechanism of FLH-induced early flowering is not understood. Here, the integration of FLH activity into the known flowering time pathways is described using molecular and genetic approaches. The identification of molecular markers that co-segregated with the FLH locus allowed the generation of multiple combinations of FLH alleles with mutations in flowering time genes in different flowering pathways. Combining an early flowering FLH allele with mutations in vernalization pathway genes that regulate FLC expression revealed that FLH appears to act in parallel to FLC. Surprisingly, the early flowering allele of FLH requires the floral integrator FD, but not FT, to accelerate flowering. This suggests a model in which some alleles of FLH are able to affect the FD-dependent activity of the floral activator complex.