β-Cyclocitral is a conserved root growth regulator

Natural compounds capable of increasing root depth and branching are desirable tools for enhancing stress tolerance in crops. We devised a sensitized screen to identify natural metabolites capable of regulating root traits in Arabidopsis. beta-Cyclocitral, an endogenous root compound, was found to promote cell divisions in root meristems and stimulate lateral root branching. beta-Cyclocitral rescued meristematic cell divisions in ccd1ccd4 biosynthesis mutants, and beta-cyclocitral-driven root growth was found to be independent of auxin, brassinosteroid, and reactive oxygen species signaling pathways. beta-Cyclocitral had a conserved effect on root growth in tomato and rice and generated significantly more compact crown root systems in rice. Moreover, beta-cyclocitral treatment enhanced plant vigor in rice plants exposed to salt-contaminated soil. These results indicate that beta-cyclocitral is a broadly effective root growth promoter in both monocots and eudicots and could be a valuable tool to enhance crop vigor under environmental stress.