Submitted to: Chronica Horticulturae
Publication Type: Review Article
Publication Acceptance Date: July 8, 2011
Publication Date: August 1, 2011
Citation: Reid, M.S., Jiang, C. 2011. Florigen unmasked - exciting prospects for horticulture. Chronica Horticulturae. 51:7-9.
The pioneer work of Garner and Allard, who coined the term “photoperiod” to describe the dramatic effects of day length on flowering of many plants, led to the widespread commercial use of photoperiod modification to control flowering in plants, particularly ornamentals. M.K. Chailakhyan suggested that the flowering stimulus was transmitted from the leaves to the shoot apex by a phloem-transmitted mobile stimulus he named “florigen.” This hypothesis spurred seven decades of research to identify the elusive “hormone.” Analysis of the flowering mutants of Arabidopsis thaliana, a facultative long-day plant, led to the identification of a photoperiodic pathway that results in flower induction. Now one component of that pathway, Flowering Locus T (FT), has been identified as the gene encoding the mobile flowering stimulus, florigen. The 20 kDa FT protein has been detected in phloem sap of cucurbits, and over-expression of FT overcomes the photoperiodic requirement in a short-day cucurbit, Cucurbita moschata. Similarly over-expression of FT or its orthologs results in precocious flowering in tobacco and tomato, tuberization in potato, complements flowering mutants, and induces flowering of transgenic chrysanthemums in vitro. Horticulturists can look forward to new strategies for controlling flowering, tuberization, dormancy and plant architecture stemming from this exciting discovery.