title: ABA-dependent control of GIGANTEA signalling enables drought escape via up-regulation of FLOWERING LOCUS T in Arabidopsis thaliana.
abstract: One strategy deployed by plants to endure water scarcity is to accelerate the transition to flowering adaptively via the drought escape (DE) response. In Arabidopsis thaliana, activation of the DE response requires the photoperiodic response gene GIGANTEA (GI) and the florigen genes FLOWERING LOCUS T (FT) and TWIN SISTER OF FT (TSF). The phytohormone abscisic acid (ABA) is also required for the DE response, by promoting the transcriptional up-regulation of the florigen genes. The mode of interaction between ABA and the photoperiodic genes remains obscure. In this work we use a genetic approach to demonstrate that ABA modulates GI signalling and consequently its ability to activate the florigen genes. We also reveal that the ABA-dependent activation of FT, but not TSF, requires CONSTANS (CO) and that impairing ABA signalling dramatically reduces the expression of florigen genes with little effect on the CO transcript profile. ABA signalling thus has an impact on the core genes of photoperiodic signalling GI and CO by modulating their downstream function and/or activities rather than their transcript accumulation. In addition, we show that as well as promoting flowering, ABA simultaneously represses flowering, independent of the florigen genes. Genetic analysis indicates that the target of the repressive function of ABA is the flowering-promoting gene SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1), a transcription factor integrating floral cues in the shoot meristem. Our study suggests that variations in ABA signalling provide different developmental information that allows plants to co-ordinate the onset of the reproductive phase according to the available water resources.
authors.affiliation: Department of BioSciences, Università degli Studi di Milano, Via Celoria 26, 20133, Milan, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Riboni
authors.affiliation: Department of BioSciences, Università degli Studi di Milano, Via Celoria 26, 20133, Milan, Italy.
authors.forename: Alice
authors.initials: A
authors.lastname: Robustelli Test
authors.affiliation: Department of BioSciences, Università degli Studi di Milano, Via Celoria 26, 20133, Milan, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Galbiati
authors.affiliation: Department of BioSciences, Università degli Studi di Milano, Via Celoria 26, 20133, Milan, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Tonelli
authors.affiliation: Department of BioSciences, Università degli Studi di Milano, Via Celoria 26, 20133, Milan, Italy lucio.conti@unimi.it.
authors.forename: Lucio
authors.identifier: 0000-0002-7837-4227
authors.initials: L
authors.lastname: Conti
mesh_terms: D000040:Abscisic Acid / Q000502:physiology*; D017360:Arabidopsis / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000502:physiology*; D003681:Dehydration; D035264:Flowers / Q000254:growth & development; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D026161:MADS Domain Proteins / Q000502:physiology; D010937:Plant Growth Regulators / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D015854:Up-Regulation
chemical_list: C419046:AGL20 protein, Arabidopsis; D029681:Arabidopsis Proteins; C418905:FT protein, Arabidopsis; C121183:GI protein, Arabidopsis; D026161:MADS Domain Proteins; D010937:Plant Growth Regulators; D000040:Abscisic Acid
keywords: Abscisic acid (ABA); adaptation; drought stress; florigen expression; flowering; photoperiod.