GA4 Is the Active Gibberellin in the Regulation of<i>LEAFY</i>Transcription and<i>Arabidopsis</i>Floral Initiation

Eriksson, Sven; Böhlenius, Henrik; Moritz, Thomas; Nilsson, Ove

doi:10.1105/tpc.106.042317

Cited by 330 publications

(296 citation statements)

References 64 publications

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“…Because in rice GA2ox1 expression below the vegetative meristem was substantially reduced after floral induction, the authors speculated that GA 2-oxidases have a regulatory function in the floral transition (Sakamoto et al, 2001), a hypothesis further elaborated on by King and Evans (2003) to account for the effects of various applied GAs on the floral transition in Lolium temulentum. However, Eriksson et al (2006) found that GA2ox4 transcript abundance rose as the levels of GA 4 and LEAFY mRNA increased in the shoot apex during the floral transition in SDs, consistent with a feed-forward activation of GA2ox4 by the increasing GA levels, suggesting that, in Arabidopsis, C 19 -GA 2-oxidase activity around the meristem does not play an active role in the floral transition, but acts constantly to prevent low amounts of GAs, possibly originating from the young leaf primordia, from entering the meristem region.…”

Section: Discussion C 19 -Ga 2-oxidase Activity In Arabidopsismentioning

confidence: 99%

Genetic Analysis Reveals That C19-GA 2-Oxidation Is a Major Gibberellin Inactivation Pathway inArabidopsis

et al. 2008

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Bioactive hormone concentrations are regulated both at the level of hormone synthesis and through controlled inactivation. Based on the ubiquitous presence of 2β-hydroxylated gibberellins (GAs), a major inactivating pathway for the plant hormone GA seems to be via GA 2-oxidation. In this study, we used various approaches to determine the role of C19-GA 2-oxidation in regulating GA concentration and GA-responsive plant growth and development. We show that Arabidopsis thaliana has five C19-GA 2-oxidases, transcripts for one or more of which are present in all organs and at all stages of development examined. Expression of four of the five genes is subject to feed-forward regulation. By knocking out all five Arabidopsis C19-GA 2-oxidases, we show that C19-GA 2-oxidation limits bioactive GA content and regulates plant development at various stages during the plant life cycle: C19-GA 2-oxidases prevent seed germination in the absence of light and cold stimuli, delay the vegetative and floral phase transitions, limit the number of flowers produced per inflorescence, and suppress elongation of the pistil prior to fertilization. Under GA-limited conditions, further roles are revealed, such as limiting elongation of the main stem and side shoots. We conclude that C19-GA 2-oxidation is a major GA inactivation pathway regulating development in Arabidopsis.

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Section: Discussion C 19 -Ga 2-oxidase Activity In Arabidopsismentioning

confidence: 99%

Genetic Analysis Reveals That C19-GA 2-Oxidation Is a Major Gibberellin Inactivation Pathway inArabidopsis

et al. 2008

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“…As mentioned previously, GAs promote flowering through the activation of SOC1 and LFY both in LD and SD 19,20,25,26 , therefore we compared the expression levels of these positive floral activators in wild-type and tem1-1 tem2-2 mutant plants grown under SD and LD before their respective wild-type floral induction times. At all time points tested, SOC1 and LFY, as well as GA3OX1, were upregulated in the tem1-1 tem2-2 double mutant with a 2-3 fold increase (Fig.…”

Section: Soc1 and Lfy Are Upregulated In Tem Mutants Under Ld And Sdmentioning

confidence: 99%

“…In SD, flowering is mainly promoted by the plant hormones GAs through the activation of the floral integrator SOC1 8 and the floral meristem identity gene LFY in the apical meristem 19 , although they also seem to have a role in LD 20,25,26 . We found that ga3ox1 mutation delays the early flowering of tem1 tem2 double mutants, as in LD tem1-1 tem2-2 plants generated 6.53 ± 0.80 rosette leaves whereas tem1 tem2 ga3ox1 triple mutant plants flowered after producing 8.09 ± 0.66 rosette leaves (Table 1).…”

Section: Tem Silencing Affects Flowering and Hypocotyl Elongationmentioning

confidence: 99%

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TEMPRANILLO genes link photoperiod and gibberellin pathways to control flowering in Arabidopsis

et al. 2012

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In Arabidopsis, FLOWERING LOCUS T (FT) promotes flowering in response to long days in the photoperiod pathway, while signalling downstream gibberellin (GA) perception is critical for flowering under short days. Previously we have established that the TEMPRANILLO (TEM) genes have a pivotal role in the direct repression of FT. Here we show that TEM genes directly regulate the expression of the GA 4 biosynthetic genes GA 3-oxidase1 and 2 (GA3OX1 and GA3OX2). Plants overexpressing TEM genes resemble GA-deficient mutants, and conversely, TEM downregulation give rise to elongated hypocotyls perhaps as a result of an increase in GA content. We consistently find that TEm1 represses GA3OX1 and GA3OX2 by directly binding a regulatory region positioned in the first exon. our results indicate that TEM genes seem to link the photoperiod and GA-dependent flowering pathways, controlling floral transition under inductive and non-inductive day lengths through the regulation of the floral integrators.

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“…The growth hormone GA is another endogenous signal that promotes flowering in Arabidopsis (Eriksson et al, 2006;Andrés et al, 2014). To investigate whether C. hirsuta petal number varies in response to GA levels, we treated C. hirsuta with 0, 0.1, or 10 mM GA 3 .…”

Section: Petal Number Regulation By Endogenous Signalsmentioning

confidence: 99%

Seasonal Regulation of Petal Number

et al. 2017

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Four petals characterize the flowers of most species in the Brassicaceae family, and this phenotype is generally robust to genetic and environmental variation. A variable petal number distinguishes the flowers of Cardamine hirsuta from those of its close relative Arabidopsis (Arabidopsis thaliana), and allelic variation at many loci contribute to this trait. However, it is less clear whether C. hirsuta petal number varies in response to seasonal changes in environment. To address this question, we assessed whether petal number responds to a suite of environmental and endogenous cues that regulate flowering time in C. hirsuta. We found that petal number showed seasonal variation in C. hirsuta, such that spring flowering plants developed more petals than those flowering in summer. Conditions associated with spring flowering, including cool ambient temperature, short photoperiod, and vernalization, all increased petal number in C. hirsuta. Cool temperature caused the strongest increase in petal number and lengthened the time interval over which floral meristems matured. We performed live imaging of early flower development and showed that floral buds developed more slowly at 15°C versus 20°C. This extended phase of floral meristem formation, coupled with slower growth of sepals at 15°C, produced larger intersepal regions with more space available for petal initiation. In summary, the growth and maturation of floral buds is associated with variable petal number in C. hirsuta and responds to seasonal changes in ambient temperature.

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GA4 Is the Active Gibberellin in the Regulation ofLEAFYTranscription andArabidopsisFloral Initiation

Cited by 330 publications

References 64 publications

Genetic Analysis Reveals That C19-GA 2-Oxidation Is a Major Gibberellin Inactivation Pathway inArabidopsis

Genetic Analysis Reveals That C19-GA 2-Oxidation Is a Major Gibberellin Inactivation Pathway inArabidopsis

TEMPRANILLO genes link photoperiod and gibberellin pathways to control flowering in Arabidopsis

Seasonal Regulation of Petal Number

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