Same organ, different place – conserved regulation of a transient stem-cellstate in the initiation of multiple root types
Plantsadjust their post-embryonic growth in response to environmental cues by formingnew organs in different developmental contexts. Underground lateral rootsinitiate from prepatterned cells in the main root, but cells can also bypassthe root/shoot trajectory separation and generate shoot-borne-roots through anunknown mechanism. We mapped tomato (Solanum lycoperiscum)shoot-borne-roots development at single-cell resolution and show that theyinitiate from differentiated phloem-associated cells via a unique transitionalstem-cell-like state. This state required the activity of a transcriptionfactor which we named SHOOTBORNE ROOTLESS (SBRL). SBRL functionand regulation was deeply conserved in angiosperms and phylogenetic analysisrevealed that it arose as an ancient duplicated superlocus with its paralogsshowing root-type-specific transient expression in wound-induced and lateralroot initiation. We propose a new model for root initiation in plants, wherethe activation of a common transitional stem-cells is controlled by multiplecontext-specific regulators. Thus, the evolutionary expansion of theseregulators underlies the remarkable plasticity of plant root systems.
Host: Sagi Levy and Sigal Savaldi-Goldstein