Multilevel interactions of ABA signals with the floral genes network

Plants deploy several strategies to endure remarkable levels of drought stress, including the synchronization of flowering with the rainy season to anticipate summer drought. This strategy, referred to as drought escape (DE) can also be plastically adjusted in Arabidopsis. Two signaling networks form the basic structure of DE; the photoperiodic pathway, and the phytohormone abscisic acid (ABA). However, ABA signaling has complex roles during floral transition with multiple targets and sites of action. Photoperiodic genes and ABA converge upon the transcriptional activation of the florigen gene FT. Florigen activation is mediated by CONSTANS (CO) and the study of transgenic plants over-expressing tagged versions of CO proteins in different ABA genetic backgrounds point to a post transcriptional level of regulation of CO mediated by ABA. By probing the natural genetic variation of Arabidopsis we also found a large variation in DE trait, including a major effect QTL for DE repression on chromosome 4. Combined gene editing and physiological data support the role of FRIGIDA (FRI) as the main causative candidate gene for this trait. Finally, we will discuss how ABA signals might relate to the flowering network at the shoot apical meristem via regulation of group A bZIPs factors. 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 and maximise water use.