Plant and Cell Physiology Advance Access originally published online on March 22, 2007
Plant and Cell Physiology 2007 48(4):615-625; doi:10.1093/pcp/pcm034
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Flowering in Tobacco Needs Gibberellins but is not Promoted by the Levels of Active GA1 and GA4 in the Apical Shoot
1Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-CSIC, Avda. de los Naranjos s/n, 46022 Valencia, Spain
2Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Science, S-90183 Umeå, Sweden
*Corresponding author: E-mail, ilopez{at}ibmcp.upv.es; Fax, +34 963877859.
 |
Abstract |
|---|
Flowering of Nicotiana tabacum cv Xhanti depends on gibberellins because gibberellin-deficient plants, due to overexpression of a gibberellin 2-oxidase gene (35S:NoGA2ox3) or to treatment with the gibberellin biosynthesis inhibitor paclobutrazol, flowered later than wild type. These plants also showed inhibition of the expression of molecular markers related to floral transition (NtMADS-4 and NtMADS-11). To investigate further the role of gibberellin in flowering, we quantified its content in tobacco plants during development. We found a progressive reduction in the levels of GA1 and GA4 in the apical shoot during vegetative growth, reaching very low levels at floral transition and beyond. This excludes these two gibberellins as flowering-promoting factors in the apex. The evolution of active gibberellin content in apical shoots agrees with the expression patterns of gibberellin metabolism genes: two encoding gibberellin 20-oxidases (NtGA20ox1 = Ntc12, NtGA20ox2 = Ntc16), one encoding a gibberellin 3-oxidase (NtGA3ox1 = Nty) and one encoding a gibberellin 2-oxidase (NtGA2ox1), suggesting that active gibberellins are locally synthesized. In young apical leaves, GA1 and GA4 content and the expression of gibberellin metabolism genes were rather constant. Our results support that floral transition in tobacco, in contrast to that in Arabidopsis, is not regulated by the levels of GA1 and GA4 in apical shoots, although reaching a threshold in gibberellin levels may be necessary to allow meristem competence for flowering.
Keywords: Flowering - Gibberellins - Tobacco
Abbreviations: GA2ox, gibberellin 2-oxidase; GA3ox, gibberellin 3-oxidase; GA20ox, gibberellin 20-oxidase; PCB, paclobutrazol; RT–PCR, reverse transcription–PCR
(Received December 22, 2006; Accepted March 6, 2007)
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  Y.-J. Liu, A. Nunes-Nesi, S. V. Wallstrom, I. Lager, A. M. Michalecka, F. E.B. Norberg, S. Widell, K. M. Fredlund, A. R. Fernie, and A. G. Rasmusson A Redox-Mediated Modulation of Stem Bolting in Transgenic Nicotiana sylvestris Differentially Expressing the External Mitochondrial NADPH Dehydrogenase Plant Physiology, July 1, 2009; 150(3): 1248 - 1259. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Compiled by, F. Tooke, T. Chiurugwi, and N. Battey Flowering Newsletter bibliography for 2007 J. Exp. Bot., July 18, 2008; (2008) ern109v1. [Full Text] [PDF]
|
|
|
|
 |
|
 L. Gallego-Giraldo, S. Ubeda-Tomas, C. Gisbert, J. L. Garcia-Martinez, T. Moritz, and I. Lopez-Diaz Gibberellin Homeostasis in Tobacco is Regulated by Gibberellin Metabolism Genes with Different Gibberellin Sensitivity Plant Cell Physiol., May 1, 2008; 49(5): 679 - 690. [Abstract] [Full Text] [PDF]
|
|