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Plant root architecture is developmentally plastic in response to fluctuating nutrient levels in the soil. Part of this developmental plasticity is the formation of dedicated root cells and organs to host mutualistic symbionts. Structures like nitrogen‐fixing nodules serve as alternative nutrient acquisition strategies during starvation conditions. Some root systems can also form myconodules—globular root structures that can host mycorrhizal fungi. The myconodule association is different from the wide‐spread arbuscular mycorrhization. This range of symbiotic associations provides different degrees of compartmentalisation, from the cellular to organ scale, which allows the plant host to regulate the entry and extent of symbiotic interactions. In this review, we discuss the degrees of symbiont compartmentalisation by the plant host as a developmental strategy and speculate how spatial confinement mitigates risks associated with root symbiosis. Summary statement: In this review, we aim to synthesize a picture of how plants manage microorganism associations through a common theme of compartmentalising symbiotic microbes into specific cell‐types or organs. We discuss a range of examples of symbiosis, including 'myconodules'—nodule‐like organs that host endosymbiotic fungi and, in some species, are co‐colonized with nitrogen‐fixing bacteria. The context of growth and safety trade‐offs associated with microbe engagement may help explain both extant and extinct types of endosymbiotic nodules. [ABSTRACT FROM AUTHOR]

A major challenge in developmental biology is unraveling the precise regulation of plant stem cell maintenance and the transition to a fully differentiated cell. In this review, we highlight major themes coordinating the acquisition of cell identity and subsequent differentiation in plants. Plant cells are immobile and establish position-dependent cell lineages that rely heavily on external cues. Central players are the hormones auxin and cytokinin, which balance cell division and differentiation during organogenesis. Transcription factors and miRNAs, many of which are mobile in plants, establish gene regulatory networks that communicate cell position and fate. Small peptide signaling also provides positional cues as new cell types emerge from stem cell division and progress through differentiation. These pathways recruit similar players for patterning different organs, emphasizing the modular nature of gene regulatory networks. Finally, we speculate on the outstanding questions in the field and discuss how they may be addressed by emerging technologies. [ABSTRACT FROM AUTHOR]