Natural variation and multilevel interactions between water deficit and flowering time signals

Plants deploy several strategies to endure remarkable levels of drought stress, including the synchronization of flowering time with the rainy season to anticipate summer drought. This strategy, referred to as drought escape (DE) can also be plastically adjusted in Arabidopsis. A long-standing question revolves around elucidating the molecular control of DE to gain insights into developmental plasticity in response to water deficit. The genetic dissection of DE exposed at least two major signaling networks which unfold at different temporal and tissue scales: the photoperiodic pathway, and the phytohormone abscisic acid (ABA). In the leaf, photoperiod-activated signals and ABA converge upon the transcriptional activation of the florigen gene FT. We've discovered that ABA promotes the recruitment of CONSTANS (CO) to the proximal promoter of FT, enhancing its transcriptional activation. Reduced CO recruitment in ABA-deficient mutants hampers RNAPol II occupancy at the transcription start site of FT, leading to diminished transcription. Additionally, we'll discuss our ongoing investigation into the substantial DE variability in Arabidopsis. We mapped a main effect QTL that underlies DE repression in the C24 ecotype. Using Crispr-Cas9 editing we could demonstrate the role of FRIGIDA (FRI) as the causal allele for the non-DE phenotype of C24. Furthermore, we could show that FRI action depends on the regulation of FLOWERING LOCUS C (FLC) and mutations in FLC can also recuperate DE in C24. Given that FLC governs water-saving strategies, we speculate that the balance between FLC and FT activations in various Arabidopsis accessions may play a vital role in coordinating flowering time based on prevailing watering conditions, thereby optimizing fitness.