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Gene Review

GI  -  protein GIGANTEA

Arabidopsis thaliana

Synonyms: FB, GIGANTEA, T22J18.6, T22J18_6
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Disease relevance of GI


High impact information on GI

  • Control of circadian rhythms and photoperiodic flowering by the Arabidopsis GIGANTEA gene [3].
  • Numerical simulations using the interlocking-loop model show that balancing LHY/CCA1 function against GI and other evening-expressed genes can largely account for temperature compensation in wild-type plants and the temperature-specific phenotypes of gi mutants [4].
  • At 27 degrees C, a dynamic balance between GI and LHY allows temperature compensation in wild-type plants, but circadian function is impaired in lhy and gi mutant plants [4].
  • These experiments demonstrated that GI acts between the circadian oscillator and CO to promote flowering by increasing CO and FT mRNA abundance [5].
  • In contrast, ELF3 negatively regulates CO, FT, and GIGANTEA transcript levels, as the expression of all three genes is increased in elf3-1 [6].

Biological context of GI

  • Therefore, GI plays a general role in controlling circadian rhythms, and this is different from its effect on the amplitude of expression of CO and FT [5].
  • The phenotypes of spy and spy-4 gi-2 plants support the hypothesis that SPY functions with GI in pathways controlling flowering, circadian cotyledon movements, and hypocotyl elongation [1].
  • The Arabidopsis GIGANTEA (GI) gene has been shown to regulate several developmental processes, including photoperiod-mediated flowering, phytochrome B signaling, circadian clock, and carbohydrate metabolism [7].
  • This study provides evidence that down-regulation of the GI gene by co-suppression could delay bolting in a cold-sensitive long-day (LD) plant [2].
  • Oxidative stress tolerance and longevity in Arabidopsis: the late-flowering mutant gigantea is tolerant to paraquat [8].

Associations of GI with chemical compounds


Regulatory relationships of GI

  • Also, we demonstrate that one of the mechanisms underlying GI protein oscillation occurs post-translationally via dark-induced proteolysis by the 26S proteasome [10].

Other interactions of GI

  • As previously reported, the gi-2 mutation affects the period length and amplitude of CCA1 and LHY expression, and GI may act through a feedback loop to maintain a proper circadian function [11].
  • Loss of GI function causes late flowering and reduces CO and FT RNA levels [1].
  • ZTL overexpression does not delay flowering through changes in GIGANTEA or FLAVIN-BINDING, KELCH REPEAT, F-BOX levels, but through a ZTL-mediated reduction in CO expression [6].
  • The analysis of mutants of the photoperiod pathway showed epistasis of co and gi to the CRY2 alleles, indicating that cry2 needs the product of CO and GI genes to promote flowering [12].
  • These cDNAs included a rice homolog of Arabidopsis GIGANTEA (GI), lir1, and a gene for myo-inositol 1-phosphate synthase, all of which were previously shown to be under the control of circadian clocks [13].


  1. SPINDLY and GIGANTEA interact and act in Arabidopsis thaliana pathways involved in light responses, flowering, and rhythms in cotyledon movements. Tseng, T.S., Salomé, P.A., McClung, C.R., Olszewski, N.E. Plant Cell (2004) [Pubmed]
  2. Expression of an antisense GIGANTEA (GI) gene fragment in transgenic radish causes delayed bolting and flowering. Curtis, I.S., Nam, H.G., Yun, J.Y., Seo, K.H. Transgenic Res. (2002) [Pubmed]
  3. Control of circadian rhythms and photoperiodic flowering by the Arabidopsis GIGANTEA gene. Park, D.H., Somers, D.E., Kim, Y.S., Choy, Y.H., Lim, H.K., Soh, M.S., Kim, H.J., Kay, S.A., Nam, H.G. Science (1999) [Pubmed]
  4. The molecular basis of temperature compensation in the Arabidopsis circadian clock. Gould, P.D., Locke, J.C., Larue, C., Southern, M.M., Davis, S.J., Hanano, S., Moyle, R., Milich, R., Putterill, J., Millar, A.J., Hall, A. Plant Cell (2006) [Pubmed]
  5. Distinct roles of GIGANTEA in promoting flowering and regulating circadian rhythms in Arabidopsis. Mizoguchi, T., Wright, L., Fujiwara, S., Cremer, F., Lee, K., Onouchi, H., Mouradov, A., Fowler, S., Kamada, H., Putterill, J., Coupland, G. Plant Cell (2005) [Pubmed]
  6. Independent roles for EARLY FLOWERING 3 and ZEITLUPE in the control of circadian timing, hypocotyl length, and flowering time. Kim, W.Y., Hicks, K.A., Somers, D.E. Plant Physiol. (2005) [Pubmed]
  7. Involvement of GIGANTEA gene in the regulation of the cold stress response in Arabidopsis. Cao, S., Ye, M., Jiang, S. Plant Cell Rep. (2005) [Pubmed]
  8. Oxidative stress tolerance and longevity in Arabidopsis: the late-flowering mutant gigantea is tolerant to paraquat. Kurepa, J., Smalle, J., Van Montagu, M., Inzé, D. Plant J. (1998) [Pubmed]
  9. Novel roles for GIGANTEA revealed under environmental conditions that modify its expression in Arabidopsis and Medicago truncatula. Paltiel, J., Amin, R., Gover, A., Ori, N., Samach, A. Planta (2006) [Pubmed]
  10. Arabidopsis GIGANTEA protein is post-transcriptionally regulated by light and dark. David, K.M., Armbruster, U., Tama, N., Putterill, J. FEBS Lett. (2006) [Pubmed]
  11. RFI2, a RING-domain zinc finger protein, negatively regulates CONSTANS expression and photoperiodic flowering. Chen, M., Ni, M. Plant J. (2006) [Pubmed]
  12. The role of cryptochrome 2 in flowering in Arabidopsis. El-Din El-Assal, S., Alonso-Blanco, C., Peeters, A.J., Wagemaker, C., Weller, J.L., Koornneef, M. Plant Physiol. (2003) [Pubmed]
  13. Isolation of rice genes possibly involved in the photoperiodic control of flowering by a fluorescent differential display method. Hayama, R., Izawa, T., Shimamoto, K. Plant Cell Physiol. (2002) [Pubmed]
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