Arabidopsis BTB-A2s Play a Key Role in Drought Stress.

Simple Summary: Given that drought stress may particularly threaten plant survival and crop yields, plants have developed sophisticated adaptive strategies including drought tolerance, escape, and avoidance strategies, for dealing with drought stress. Abscisic acid has been widely acknowledged as a principal signaling molecule in plants responding to drought, reducing water loss by prompting stomatal closure while activating various stress-responsive genes. Broad-complex, Tramtrack, and Bric-à-brac (BTB) proteins in plants are important for plant growth and stress responses. The Arabidopsis btb-a2.1/2/3 mutant confers drought tolerance by modulating plant growth parameters, physiology, and gene expression. Overall, AtBTB-A2s negatively regulate drought tolerance by suppressing stomatal closure and weakening ABA signaling. The results revealed the new physiological activity of AtBTB-A2s within Arabidopsis and the possible mechanism that mediates ABA-dependent signaling pathways during drought stress. Drought stress significantly impacts plant growth, productivity, and yield, necessitating a swift fine-tuning of pathways for adaptation to harsh environmental conditions. This study explored the effects of Arabidopsis BTB-A2.1, BTB-A2.2, and BTB-A2.3, distinguished by their exclusive possession of the Broad-complex, Tramtrack, and Bric-à-brac (BTB) domain, on the negative regulation of drought stress mediated by abscisic acid (ABA) signaling. Promoter analysis revealed the presence of numerous ABA-responsive and drought stress-related cis-acting elements within the promoters of AtBTB-A2.1, AtBTB-A2.2, and AtBTB-A2.3. The AtBTB-A2.1, AtBTB-A2.2, and AtBTB-A2.3 transcript abundances increased under drought and ABA induction according to qRT-PCR and GUS staining. Furthermore, the Arabidopsis btb-a2.1/2/3 triple mutant exhibited enhanced drought tolerance, supporting the findings from the overexpression studies. Additionally, we detected a decrease in the stomatal aperture and water loss rate of the Arabidopsis btb-a2.1/2/3 mutant, suggesting the involvement of these genes in repressing stomatal closure. Importantly, the ABA signaling-responsive gene levels within Arabidopsis btb-a2.1/2/3 significantly increased compared with those in the wild type (WT) under drought stress. Based on such findings, Arabidopsis BTB-A2s negatively regulate drought stress via the ABA signaling pathway. [ABSTRACT FROM AUTHOR]