Differential TOR activation and cell proliferation in <i>Arabidopsis</i> root and shoot apexes

Abstract

Significance The modulation of growth and development is central to sessile plants. Shoot and root meristems share almost identical molecular machineries but are responsible for different types of aboveground and underground organogenesis. How two such highly similar biological systems respond to different environmental cues and regulate distinct developmental programs remains largely unknown. We report that, in harmony with nature, the shoot, but not the root, demands light for the activation of cell proliferation during organogenesis. We decipher the underlying mechanism that light is necessary for continuous auxin biosynthesis only in the shoot, but not the root, to activate target of rapamycin (TOR) kinase signaling. We further elucidate an auxin-Rho-related protein 2 (ROP2)-TOR-transcription factors E2Fa,b signaling cascade that integrates different environmental signals to orchestrate plant growth and development.