Time measurement and the control of flowering in plants

Samach, Alon; Coupland, George

doi:10.1002/(sici)1521-1878(200001)22:1<38::aid-bies8>3.0.co;2-l

Cited by 130 publications

(39 citation statements)

References 90 publications

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“…Overall, despite recent speculative claims to the contrary (Colasanti and Sunderasan, 2000;Samach and Coupland, 2000), our studies show that, for L. temulentum at least, GAs may serve as LD flowering signals. Also, our findings provide a novel and more dynamic view than has been considered previously to explain the role of GAs in floral evocation and inflorescence differentiation.…”

Section: Gas Associated With Inflorescence Developmentcontrasting

confidence: 92%

Long-Day Induction of Flowering in Lolium temulentumInvolves Sequential Increases in Specific Gibberellins at the Shoot Apex

et al. 2001

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One challenge for plant biology has been to identify floral stimuli at the shoot apex. Using sensitive and specific gas chromatography-mass spectrometry techniques, we have followed changes in gibberellins (GAs) at the shoot apex during long day (LD)-regulated induction of flowering in the grass Lolium temulentum. Two separate roles of GAs in flowering are indicated. First, within 8 h of an inductive LD, i.e. at the time of floral evocation, the GA 5 content of the shoot apex doubled to about 120 ng g Ϫ1 dry weight. The concentration of applied GA 5 required for floral induction of excised apices (R.W. King, C. Blundell, L.T. Evans [1993] Aust J Plant Physiol 20: 337-348) was similar to that in the shoot apex. Leaf-applied [ 2 H 4 ] GA 5 was transported intact from the leaf to the shoot apex, flowering being proportional to the amount of GA 5 imported. Thus, GA 5 could be part of the LD stimulus for floral evocation of L. temulentum or, alternatively, its increase at the shoot apex could follow import of a primary floral stimulus. Later, during inflorescence differentiation and especially after exposure to additional LD, a second GA action was apparent. The content of GA 1 and GA 4 in the apex increased greatly, whereas GA 5 decreased by up to 75%. GA 4 applied during inflorescence differentiation strongly promoted flowering and stem elongation, whereas it was ineffective for earlier floral evocation although it caused stem growth at all times of application. Thus, we conclude that GA 1 and GA 4 are secondary, late-acting LD stimuli for inflorescence differentiation in L. temulentum.Plants of Lolium temulentum remain vegetative when grown in short days (SD), but flower after exposure of their leaves to a single long day (LD). The leaf gibberellin (GA) content increases in LD (Gocal et al., 1999) and applied GAs can cause flowering in noninductive SD (Evans, 1964;Pharis et al., 1987;Evans et al., 1990). Thus, GAs mimic LD responses and they could be a transmissible endogenous floral stimulus in this LD plant. A number of other LD plants but not all (for summary, see Metzger, 1995) flower in response to GA, and recent genetic and molecular studies with Arabidopsis support such a role for endogenous GAs in flowering in LD (Wilson et al., 1992;Weigel and Nilsson, 1995;Blásquez et al., 1997). Furthermore, where there are effects of LD exposure on stem elongation there are clear increases in the GA content of leaves, petioles, and shoot tips (Talon and Zeevaart, 1990;Talon et al., 1991;Zeevaart et al., 1993).Inflorescence initiation in L. temulentum after one LD precedes any acceleration of stem elongation. Therefore, if GAs were to play a role endogenously in floral evocation, they should have little effect on stem elongation. From application studies, we previously identified a number of GAs, including GA 5 , that meet this criterion of inducing flowering but with little or no effect on stem elongation (Evans et al., 1990(Evans et al., , 1994a(Evans et al., , 1994b. However, in a broad context, three lines of evi...

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Section: Gas Associated With Inflorescence Developmentcontrasting

confidence: 92%

Long-Day Induction of Flowering in Lolium temulentumInvolves Sequential Increases in Specific Gibberellins at the Shoot Apex

et al. 2001

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“…In Arabidopsis thaliana, the circadian clock is involved in photoperiodic timing of flowering, with many flowering genes exhibiting circadian rhythmicity (Samach and Coupland 2000;Hayama and Coupland 2003). GIGANTEA (GI), is an Arabidopsis clock protein that links the circadian pacemaker and the photoperiodic flowering response through interaction with COSTANT (CO) and FLOWER-ING LOCUS T (FT) (Yanovsky and Kay 2003;Mizoguchi et al 2005).…”

Section: Role Of Mirna In the Circadian Clockmentioning

confidence: 99%

The role of microRNAs (miRNA) in circadian rhythmicity

Pegoraro

Tauber

2008

J Genet

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MicroRNA (miRNA) is a recently discovered new class of small RNA molecules that have a significant role in regulating gene and protein expression. These small RNAs (∼22 nt) bind to 3 untranslated regions (3 UTRs) and induce degradation or repression of translation of their mRNA targets. Hundreds of miRNAs have been identified in various organisms and have been shown to play a significant role in development and normal cell functioning. Recently, a few studies have suggested that miRNAs may be an important regulators of circadian rhythmicity, providing a new dimension (posttranscriptional) of our understanding of biological clocks. Here, we describe the mechanisms of miRNA regulation, and recent studies attempting to identify clock miRNAs and their function in the circadian system. [Pegoraro M. and Tauber E. 2008 The role of microRNAs (miRNA) in circadian rhythmicity. J. Genet. 87,[505][506][507][508][509][510][511]

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“…As a facultative long-day (LD) plant, Arabidopsis flowers earlier under LD conditions than under short-day (SD) conditions. Forward genetics in A. thaliana have identified the GI-CO-FT hierarchy as the canonical genetic pathway promoting flowering specifically under LD conditions (5,7,8). In this pathway, GI (GIGANTEA) can be considered the output point of the circadian clock to control flowering by regulating CONSTANS (CO) expression in the right phase, which activates expression of FT and TSF (TWIN SISTER OF FT) in the companion cells of the phloem within the vascular tissue (2, 9).…”

mentioning

confidence: 99%

“…Plants use the circadian clock as the timekeeping mechanism to measure day length and to ensure flowering at the proper season (5,6). As a facultative long-day (LD) plant, Arabidopsis flowers earlier under LD conditions than under short-day (SD) conditions.…”

mentioning

confidence: 99%

Arabidopsis cryptochrome 1 functions in nitrogen regulation of flowering

Yuan

Zhang

Zheng

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

115

103

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The phenomenon of delayed flowering after the application of nitrogen (N) fertilizer has long been known in agriculture, but the detailed molecular basis for this phenomenon is largely unclear. Here we used a modified method of suppression-subtractive hybridization to identify two key factors involved in N-regulated flowering time control in Arabidopsis thaliana, namely ferredoxin-NADP + -oxidoreductase and the blue-light receptor cryptochrome 1 (CRY1). The expression of both genes is induced by low N levels, and their loss-offunction mutants are insensitive to altered N concentration. Low-N conditions increase both NADPH/NADP + and ATP/AMP ratios, which in turn affect adenosine monophosphate-activated protein kinase (AMPK) activity. Moreover, our results show that the AMPK activity and nuclear localization are rhythmic and inversely correlated with nuclear CRY1 protein abundance. Low-N conditions increase but high-N conditions decrease the expression of several key components of the central oscillator (e.g., CCA1, LHY, and TOC1) and the flowering output genes (e.g., GI and CO). Taken together, our results suggest that N signaling functions as a modulator of nuclear CRY1 protein abundance, as well as the input signal for the central circadian clock to interfere with the normal flowering process. T he transition from vegetative to reproductive development is a central event in the plant life cycle, which is coordinately regulated by various endogenous and external cues. In the model dicotyledonous plant species Arabidopsis thaliana, five distinct genetic pathways regulating flowering time have been established: the vernalization pathway, photoperiod pathway, gibberellin acid (GA) pathway, autonomous pathway, and endogenous (age) pathway (1). These pathways ultimately converge to regulate a set of floral integrator genes, FLOWERING LOCUS T (FT) and SUPPRESSOR OF CONSTANS 1 (SOC1), which in turn activate the expression of floral meristem identity genes to trigger the formation of flowers (2-4).Plants use the circadian clock as the timekeeping mechanism to measure day length and to ensure flowering at the proper season (5, 6). As a facultative long-day (LD) plant, Arabidopsis flowers earlier under LD conditions than under short-day (SD) conditions. Forward genetics in A. thaliana have identified the GI-CO-FT hierarchy as the canonical genetic pathway promoting flowering specifically under LD conditions (5,7,8). In this pathway, GI (GIGANTEA) can be considered the output point of the circadian clock to control flowering by regulating CONSTANS (CO) expression in the right phase, which activates expression of FT and TSF (TWIN SISTER OF FT) in the companion cells of the phloem within the vascular tissue (2, 9). FT and TSF proteins act as the long-sought florigens that move from leaves to the apical meristem to induce genes required for reproductive development (2-4). Both GI and CO are regulated by the circadian clock and by light signaling simultaneously and at both transcriptional and posttranscriptional levels, to en...

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Time measurement and the control of flowering in plants

Cited by 130 publications

References 90 publications

Long-Day Induction of Flowering in Lolium temulentumInvolves Sequential Increases in Specific Gibberellins at the Shoot Apex

Long-Day Induction of Flowering in Lolium temulentumInvolves Sequential Increases in Specific Gibberellins at the Shoot Apex

The role of microRNAs (miRNA) in circadian rhythmicity

Arabidopsis cryptochrome 1 functions in nitrogen regulation of flowering

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