PMID- 33865238 OWN - NLM STAT- MEDLINE VI - 72 IP - 12 TI - Cell identity specification in plants: lessons from flower development. PG - 4202-4217 CI - © The Author(s) 2021. Published by Oxford University Press on behalf of the Society for Experimental Biology. LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't PT - Review PL - England TA - J Exp Bot JT - Journal of experimental botany JID - 9882906 IS - 1460-2431 (Electronic) LID - 10.1093/jxb/erab110 [doi] FAU - Xu, Xiaocai AU - Xu X AD - Plant Cell and Molecular Biology, Institute of Biology, Humboldt-Universität zu Berlin, Berlin, Germany. FAU - Smaczniak, Cezary AU - Smaczniak C AD - Plant Cell and Molecular Biology, Institute of Biology, Humboldt-Universität zu Berlin, Berlin, Germany. FAU - Muino, Jose M AU - Muino JM AD - Systems Biology of Gene Regulation, Humboldt-Universität zu Berlin, Institute of Biology, Berlin, Germany. FAU - Kaufmann, Kerstin AU - Kaufmann K AUID- ORCID: 0000-0001-7960-6256 AD - Plant Cell and Molecular Biology, Institute of Biology, Humboldt-Universität zu Berlin, Berlin, Germany. IS - 0022-0957 (Linking) RN - 0 (Transcription Factors) SB - IM MH - Cell Differentiation MH - Flowers/metabolism MH - Gene Expression Regulation, Developmental MH - *Gene Expression Regulation, Plant MH - *Plants/genetics/metabolism MH - Transcription Factors/genetics/metabolism OTO - NOTNLM OT - *Cell lineage OT - *cellular differentiation OT - *flower development OT - *phytohormone OT - *plant cell type OT - *positional regulation OT - *transcription factor PMC - PMC8163053 DCOM- 20210709 LR - 20210709 DP - 20210528 AB - Multicellular organisms display a fascinating complexity of cellular identities and patterns of diversification. The concept of 'cell type' aims to describe and categorize this complexity. In this review, we discuss the traditional concept of cell types and highlight the impact of single-cell technologies and spatial omics on the understanding of cellular differentiation in plants. We summarize and compare position-based and lineage-based mechanisms of cell identity specification using flower development as a model system. More than understanding ontogenetic origins of differentiated cells, an important question in plant science is to understand their position- and developmental stage-specific heterogeneity. Combinatorial action and crosstalk of external and internal signals is the key to cellular heterogeneity, often converging on transcription factors that orchestrate gene expression programs.