Among the different environmental
factors influencing plant development, the effects of water scarcity
are extremely relevant in today’s science for their implications with the ongoing climate change. Under
natural conditions, plants can evade water deficit by synchronising the onset of reproductive
development with the rainy season. In temperate climates, characterised by dry summers, this usually
involves the selection for early flowering genotypes that can effectively escape the summer drought.
Such drought escape strategy (DE) can be adaptive. This means that upon drought stress some plants
can utilise drought signals as a cue to hasten their life cycle, thereby anticipating potentially lethal stress
Our work is centred upon the study of the molecular events underpinning the DE phenomenon in
Arabidopsis with the long-term goal of revealing their conservation in crops. Two signalling components
form the basic structure of the DE response; the photoperiodic gene GIGANTEA (GI), and the droughtrelated
phytohormone abscisic acid (ABA). GI and ABA converge upon the transcriptional activation
of the florigen genes FT and TSF. The activation of FT is usually mediated by CONSTANS (CO). I will
thus discuss the potential ABA-dependent mode of activation of GI signaling and its connection with
CO function in the leaf. Another related topic pertains the regulation of ABA targets outside the leaf and
their role in the floral transi tion. The study of mutants defective in ABA signalling suggests that ABA
has multiple roles in flowering, some of which are exerted in the shoot apical meristem. In this spatial
context, I plan to illustrate the role of a class of ABA-regulated bZIP transcription factors which are
structurally related to the flowering protein FD.
In summary, besides the key role upstream of FT, ABA is connected with the flowering network at
multiple points. Since contrasting flowering responses have been reported in nature and in crops under
varying drought scenarios, our data suggest that plants may utilize ABA signals in different ways to
coordinate flowering time according to the prevailing watering conditions.