ABA-induced MYB transcriptional module regulates the differentiation trajectory of chickpea exodermis

Abscisic acid (ABA) regulates plant responses to stress and influences the differentiation of root barrier cell types, such as the endodermis and exodermis. Despite the importance of the exodermis in limiting water and solute fluxes, its regulation remains poorly understood in legumes. Here, we characterize the ABA-induced suberization and lignification of root tissues across eight galegoid legumes. Chickpea exhibited suberin deposition specifically in the outermost cortex, forming a functional apoplastic barrier. Transcriptomics of chickpea roots revealed ABA-induced programs that were temporally separated, specifically, a rapid program with the general ABA response, and a delayed program of suberin biosynthesis. We identified putative MYB transcription factors that link the ABA response to the suberin biosynthesis in chickpea. Single-cell RNA-seq of chickpea roots uncovered putative cell-type-specific regulatory networks, suggesting that ABA-induced suberization in the exodermis is mediated by the canonical ABA signaling inducing the expression of suberin-regulating MYBs.