How meristems shape plant architecture in cereals.

Meristems are major determinants of plant architecture, plant diversification and acclimation to environmental stresses. Moreover, meristems play also a major role during crop domestication and are fundamentally important for the productivity of crop plants as they directly determine biomass and grain yield. While vegetative meristems shape the basic plant body plan and produce all above- and below-ground parts of plants, some vegetative meristems transit to reproductive meristems forming sexual organs and germ cells. Most knowledge about plant meristems was generated using the model Arabidopsis. Compared to Arabidopsis, architecture of grasses or cereals including crops like maize, wheat, barley, rice and sorghum is more complex: cereals produce additional organs like a coleoptile, seminal roots originating from the scutellar nodes in the embryo and shoot-borne crown roots as well as highly complex inflorescence meristems with meristem types absent in eudicots. Moreover, studies in cereals indicated that paradigms based on studies using Arabidopsis are not universally applicable. This review therefore aims to provide a comprehensive overview about the initiation, establishment, maintenance and function of the various cereal meristems and their stem cell niches that shape our most important crop plants. Stem cell-like systems involved in leaf pattering and germline formation are also considered. A focus is also on the significant progress that has been made recently using novel tools to elucidate the gene regulatory networks (GRNs) underlying the development and function of the various cereal meristems.