Gibberellins and the floral transition in Sinapis alba

Abstract

In many plants the transition from vegetative growth to flowering is controlled by environmental cues. One of these cues is day length or photoperiod, which synchronizes flowering of many species with the changing seasons. Recently, advances have been made in understanding the molecular mechanisms that confer photoperiodic control of flowering and, in particular, how inductive events occurring in the leaf, where photoperiod is perceived, are linked to floral evocation that takes place at the shoot apical meristem. We discuss recent data obtained using molecular genetic approaches on the function of regulatory proteins that control flowering time in Arabidopsis thaliana . These data are compared with the results of physiological analyses of the floral transition, which were performed in a range of species and directed towards identification of the transmitted floral singals.

A physiological overview of the genetics of flowering time control

“…At later stages of the transition, other compounds come into play, such as GA 1 /GA 4 (King and Evans, 2003) and sucrose (Périlleux and Bernier, 1997). GA 5 is unlikely, however, to be a universal ‘florigen’, as it is not detected in extracts of florally induced Arabidopsis and Sinapis plants (Xu et al ., 1997; Corbesier et al ., 2004).…”

“…Extra‐nitrate is, on the other hand, presumably converted into glutamine (Gln) and putrescine (Put), as these compounds are later exported in greater amounts in the phloem by induced leaves. GAs do not apparently participate in signal movements in Sinapis as their complements and levels remain unchanged in both leaves and shoot tip following floral induction (Corbesier et al ., 2004).…”

Photoperiodic flowering of Arabidopsis: integrating genetic and physiological approaches to characterization of the floral stimulus

“…Among the factors controlling the photoperiodic floral transition in S. alba , a caulescent plant belonging to the same family of the Brassicaceae as Arabidopsis , roles for sucrose, glutamine, cytokinins, auxin and putrescine were demonstrated, while GAs seem to play a minor role (reviewed in Bernier et al . 1993, 1998; Corbesier et al . 2004).…”

Flowering in Tobacco Needs Gibberellins but is not Promoted by the Levels of Active GA1 and GA4 in the Apical Shoot

“…These results cannot be extrapolated to all plant species. For instance, gibberellins do not seem to be a major flowering signal in Sinapis alba (Corbesier et al 2004). Furthermore, in Fuchsia (King et al 2000) and grapevine (Boss and Thomas 2002), gibberellins actually inhibit flowering.…”