JXB Advance Access originally published online on March 5, 2009
Journal of Experimental Botany 2009 60(7):1979-1989; doi:10.1093/jxb/erp040
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REVIEW-ARTICLE |
Gibberellin as a factor in floral regulatory networks
1Broom's Barn Research Centre, Rothamsted Research Department of Applied Crop Science, Higham, Bury St Edmunds, Suffolk IP28 6NP, UK
2Rothamsted Research, Harpenden, Herts AL5 2JQ, UK
* To whom correspondence should be addressed. E-mail: peter.hedden{at}bbsrc.ac.uk
Gibberellins (GAs) function not only to promote the growth of plant organs, but also to induce phase transitions during development. Their involvement in flower initiation in long-day (LD) and biennial plants is well established and there is growing insight into the mechanisms by which floral induction is achieved. The extent to which GAs mediate the photoperiodic stimulus to flowering in LD plants is, with a few exceptions, less clear. Despite evidence for photoperiod-enhanced GA biosynthesis in leaves of many LD plants, through up-regulation of GA 20-oxidase gene expression, a function for GAs as transmitted signals from leaves to apices in response to LD has been demonstrated only in Lolium species. In Arabidopsis thaliana, as one of four quantitative floral pathways, GA signalling has a relatively minor influence on flowering time in LD, while in SD, in the absence of the photoperiod flowering pathway, the GA pathway assumes a major role and becomes obligatory. Gibberellins promote flowering in Arabidopsis through the activation of genes encoding the floral integrators SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1), LEAFY (LFY), and FLOWERING LOCUS T (FT) in the inflorescence and floral meristems, and in leaves, respectively. Although GA signalling is not required for floral organ specification, it is essential for the normal growth and development of these organs. The sites of GA production and action within flowers, and the signalling pathways involved are beginning to be revealed.
Key words: Arabidopsis, DELLA, floral transcription factors, flower development, flower induction, gibberellin, LEAFY, Lolium, SOC1
Received 11 December 2008; Revised 29 January 2009 Accepted 2 February 2009
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