Elucidating the genetic landscape of the biphasic root growth response to abscisic acid in Arabidopsis

Root growth and branching are the major factors that influence root system architecture (RSA), and thus are critical for overall plant growth. Abscisic acid (ABA), a plant phytohormone that is synthesized in most plant tissues, can either stimulate or inhibit root morphology in a dose dependent manner. In this study, we aimed to identify specific novel genes that associated with the biphasic root response to low/high ABA concentration. A study of 262 Arabidopsis thaliana accessions was performed in a growth chamber under control and different ABA concentration levels of both 50nM and 1uM and RSA was measured. Genome-wide association studies (GWAS) together with statistical analysis was performed on our data set, and several potential genes of interest (GOIs) that might have an effect on RSA in response to ABA were discovered. The most promising genes were selected for validation of the linkage between these genes and their root phenotypes by using specific knockouts mutant plants in Colombia accession background. Our results show that under both ABA conditions, primary root elongation as well as lateral root growth was altered in some of the mutants indicating a functional role of those GOIs in ABA response. Moreover, the involvement of those genes in shaping root hydraulic architecture (root system architecture and tissue hydraulic properties that together regulate root water uptake) is being studied. Further analysis using cell, tissue and whole plant characterization of mutants/over expression lines will shed light on those important traits and its genetic regulation.