Rational design of induced regeneration via somatic embryogenesis in the absence of exogenous phytohormones

Plants have a remarkable regenerative capacity, but this varies widely among species and tissue types. Important crop cultivars show regenerative recalcitrance, which is a major obstacle for the application of modern plant propagation and breeding techniques. Regeneration generally involves empirically determined tissue culture methods that are based on the principle of inducing totipotency. Cells are first persuaded to change fate toward root stem cell-like identity and then are reprogrammed to acquire shoot fate. Alternatively, pluri- or totipotent cells can lead to the formation of a complete plantlet through somatic embryogenesis. We applied our knowledge of root stem cell niche biology to directly use the implicated stem cell factors, including RETINOBLASTOMA (RBR), SCARECROW (SCR), SHORT ROOT (SHR), and members of the AINTEGUMENTA-LIKE/PLETHORA (AIL/PLT) and WUSCHEL-related homeobox (WOX) gene families, as a tool to induce regeneration in a way similar to the principle of induced pluripotent stem cells in the animal field. We show that stem cell factors synergistically induce regeneration involving the somatic embryogenesis pathway and can break recalcitrance in Arabidopsis (Arabidopsis thaliana) and pepper (Capsicum annuum).