Divergence in the ABA gene regulatory network underlies differential growth control

The phytohormone abscisic acid (ABA) is a central regulator of acclimation to environmental stress; however, its contribution to differences in stress tolerance between species is unclear. To establish a comparative framework for understanding how stress hormone signalling pathways diverge across species, we studied the growth response of four Brassicaceae species to ABA treatment and generated transcriptomic and DNA affinity purification and sequencing datasets to construct a cross-species gene regulatory network (GRN) for ABA. Comparison of genes bound directly by ABA-responsive element binding factors suggests that cis-factors are most important for determining the target loci represented in the ABA GRN of a particular species. Using this GRN, we reveal how rewiring of growth hormone subnetworks contributes to stark differences in the response to ABA in the extremophyte Schrenkiella parvula. Our study provides a model for understanding how divergence in gene regulation can lead to species-specific physiological outcomes in response to hormonal cues. A network of ABA-responsive transcription factors emerges from a genome-wide comparative analysis of four Brassicaceae species, including Arabidopsis thaliana and extremophyte Schrenkiella parvula. Rewiring of growth hormone subnetworks might explain the different physiological responses to stress.

Automated summary

The phytohormone abscisic acid (ABA) plays a role in environmental stress acclimation, but its contribution to stress tolerance differences between species is unclear. By studying the growth response of four Brassicaceae species to ABA treatment and constructing a gene regulatory network (GRN) for ABA, this study compares the divergence of stress hormone signaling pathways across species. The study shows that cis-factors are most important in determining the target sites in the ABA GRN of a particular species. The rewiring of growth hormone subnetworks contributes to the differences in response to ABA in the extremophyte Schrenkiella parvula.