Characterization of Arabidopsis thaliana Root-Related Mutants Reveals ABA Regulation of Plant Development and Drought Resistance

The plant hormone abscisic acid (ABA) regulates many processes of plant growth and development. ABA receptors have been identified in studies of the ABA response of stomatal movement, but the underlying mechanisms of ABA-regulated root growth and development are unclear. To address these questions, we screened for Arabidopsis thaliana mutants based on the sensitivity of root growth to exogenous ABA, using ethyl methanesulfonate-mutagenized (EMS) and T-DNA insertion mutant libraries. We identified 11 mutants, termed roa1–roa11, with Root growth Overly sensitive to ABA (ROA) phenotypes, and cloned two of the ROA genes, one by thermal asymmetric interlaced PCR technology (ROA3) and the other by map-based cloning (ROA9). The roa mutants were also found to have defects in other major ABA responses, including ABA-mediated seed germination and drought resistance. The roa mutants provide crucial genetic material for further studies of ABA signaling and regulatory mechanisms in root growth and development.