A KNOX-cytokinin regulatory module predates the origin of indeterminacy (Curr. Biol.)

In vascular plants, new organs (e.g., leaves) are produced continuously from the shoot meristem, a process coined indeterminacy. The sister lineage of vascular plants, bryophytes, develop differently, ending with the formation of a determinate spore-bearing shoot (sporangium). The genetic underpinning of indeterminacy is well understood in vascular plants, but the mechanisms enabling the transition from determinacy to a vascular plant meristem still remain unclear. Here, Coudert et al. demonstrate that in the moss Physcomitrella patens, KNOX genes control stem development as well as cytokinin production, which is involved in regulating cell division. By characterizing KNOX protein functions in extant plants, this research informs our understanding of the ancestral function of these genes. This important functional unit predates the origin of vascular plants, and is derived from the common ancestor of vascular plants and bryophytes (Summary by Alex Bowles) Curr. Biol. 10.1016/j.cub.2019.06.083