Résumé
Improving crop resilience through enhanced root system architecture (RSA) is crucial in adapting to changing environmental conditions. Lateral root (LR) formation, predominantly regulated by auxin signaling pathways, is a complex process. We recently presented the first developmental atlas of LR development in the model grass species Brachypodium distachyon (Bd), revealing the reactivation of the endodermis cell cycle, contributing to the formation of root cap and columella cells in emerged LRs. Interestingly, our findings suggest that auxin signaling, indicated by DR5 promoter activity, is not evident in the phloem pole pericycle or during early LR development, but correlates with cell wall modifications during LR primordium (LRP) emergence.Conducting a comparative analysis on Bd21 and Bd21-3 accessions, we observed similar LR primordia synchronization post-root tip removal, but distinct of the LR architecture thereafter. RNAseq analysis unveiled distinct early and late responses in both accessions, with significant overlap of differentially expressed genes at later time points. Enrichment of cell-wall-related processes was observed, and patterns of cell wall remodeling gene families varied during early LR formation. Additionally, we identified several GDSL/GELP genes showing similar expression patterns during LRP formation in both Brachypodium and Arabidopsis, along with conserved GDSL protein structures. Notably, the orthologous copy of AtGELP38, identified as a suberin synthase in Arabidopsis, BdGELP38, was expressed in the endodermis overlaying LRPs and functionally rescued the absence of suberin phenotype in the gelpquint mutants. These findings shed light on conserved and divergent mechanisms in LRP development, thereby advancing our understanding of root branching regulation in plant biology research.