Species-specific function of conserved regulators in orchestrating rice root architecture

Abstract

Shoot-borne adventitious/crown roots form highly derived fibrous root system in grasses. Molecular mechanisms controlling their development remains largely unknown. We provide a genome-wide landscape of transcriptional signatures, tightly regulated auxin response, and in-depth spatio-temporal expression patterns of potential epigenetic modifiers, and transcription factors during priming and outgrowth of rice crown root primordia. Functional analyses of rice transcription factors from WUSCHEL-RELATED HOMEOBOX and PLETHORA gene families reveal their non-redundant, and species-specific roles in determining the root architecture. OsWOX10, and OsPLT1 regulate both, shoot-borne crown roots, and root-borne lateral roots, but OsPLT2 specifically controls lateral root development. OsPLT1 activates local auxin biosynthesis genes to promote crown root development. Interestingly, OsPLT genes rescue lateral root primordia outgrowth defects of Arabidopsis plt mutant, demonstrating their conserved role in root primordia outgrowth irrespective of their developmental origin. Together, our findings unveil a molecular framework of tissue trans-differentiation during root primordia establishment, leading to culmination of robust fibrous root architecture. This also suggests that conserved factors have evolved their transcription regulation to acquire species-specific function.