ERECTA signaling controls the timing of Arabidopsis Guard Cell maturation at the embryonic leaf tip

Specification of embryonic shoot stem cells via a small RNA-driven morphogenic circuit

Emerging insights into developmental programmed cell death in plants.

This review provides an integrative overview of developmental PCD across vegetative and generative stages, from reproductive development and embryogenesis to vascular differentiation, aerenchyma formation, organ shaping, senescence, and abscission, and summarizes current knowledge of the molecular, cellular, and physiological mechanisms governing dPCD.

The extracellular regulatory network and key factors governing early embryogenesis in Nicotiana tabacum.

It is reported that NtProRP1, an extracellular protein, localizes to the cell wall immediately after fertilization in Nicotiana tabacum, uncovering a new mechanism for NtProRP1 in regulating early embryogenesis and delivering a unique transcriptomic resource that advances understanding of extracellular signaling in plant embryogenesis.

A single-nucleus transcriptomic atlas reveals distinct cell identities and key regulators of cellular differentiation during early rice seed development.

The early morphogenesis of the embryo and endosperm sets the upper limit of rice grain yield; yet, the cellular dynamics and regulatory mechanisms underlying this critical stage remain largely elusive. Here, we present a single-cell atlas of developing rice seeds based on single-nucleus RNA sequencing of 67,922 high-quality nuclei from rice caryopses. Integration with bulk RNA-seq, in situ hybridization, and promoter-GUS staining enabled systematic cell-type annotation and revealed a distinct population of embryo-endosperm interface (EEI) cells occupying the boundary between the developing embryo and endosperm. Comparative analyses with maize data sets, together with trajectory inference, suggested that a subset of EEI cells shares molecular features with maize embryo-adjacent scutellum cells and shows transcriptional continuity with starchy endosperm cells. Embryo-endosperm interface cells were enriched in transport-related and developmental regulatory genes with known functions in seed development and embryogenesis. Focusing on the EEI-enriched regulator OsBZR4, we found that loss of OsBZR4 altered cellular composition and transcriptional programs during early seed development, disrupted embryonic developmental progression, and reduced the expression of embryonic genes, including OsCDP3.10 and RINO1. Together, our study provides a single-cell resolution framework for understanding early rice seed development, identifies the embryo-endosperm interface as an important cellular domain associated with embryogenesis, and offers a valuable resource for dissecting the molecular basis of seed formation in rice and related cereals.

Cell identities along the proximal-distal and micropylar-chalazal axes in the Arabidopsis heart-stage seed

• Seeds are complex reproductive organs consisting of diverse maternal and filial tissues. During development, the embryo and specialized tissues for nutrient storage required for seed germination and early seedling establishment emerge. • To explore the cellular diversity and differentiation of seeds, we performed single cell RNA-sequencing on heart stage Arabidopsis seeds and identified 20,097 cells that were grouped into ≥21 distinct cell clusters. 20 of the 21 clusters were spatially assigned by combining bioinformatic analysis, imaging reporter fusion marker lines, and spatial transcriptomics. • Our analysis revealed a high degree of differentiation of epidermal cell and inner cell layers along the rotational and axial seed axes, highlighting the importance of cell position and ontogenesis. We identified unexpected spatial domains, including a cluster marked by abscission zone-specific transcripts, and a nucellar cluster shaped by developmentally programmed cell death. Surprisingly, embryo and endosperm showed similarities in transcript profiles despite distinct and complementary functions. • In summary, our findings establish seeds as a transcriptionally complex organ with high cell type heterogeneity and provide a basis for investigating the differentiation of diverse cell layers and spatial transcript profiles.

BAM3 Is a CLE19 Receptor that Mediates a Distinct Signaling Branch Controlling Tapetum Degeneration and Pollen Wall Formation.

Pollen wall formation requires precise coordination between tapetum differentiation, metabolism, and programmed cell death. In Arabidopsis, the microspore-derived peptide CLE19 restricts tapetal activity to maintain pollen wall homeostasis, yet how CLE19 signaling achieves developmental specificity and robustness remains unclear. Here, we identify the receptor-like kinase BARELY ANY MERISTEM 3 (BAM3) as an additional receptor for CLE19. Genetic, cytological, biochemical, and transcriptomic analyses showed that disruption of BAM3 signaling impairs tapetum differentiation, secretory homeostasis, and pollen exine patterning, resulting in selective transcriptional reprogramming during anther development. Comparative transcriptomic analyses reveal that BAM3 mediates a distinct subset of CLE19-responsive genes, including both AMS-dependent pathways governing tapetal degeneration and exine biosynthesis, and AMS-independent programs associated with flavonoid metabolism and pollen wall development. Biochemical assays, structure-guided mutagenesis, and AlphaFold3 modeling further support CLE19-dependent assembly of BAM3-SERK1/2 receptor complex, revealing a conserved molecular framework for CLE19 perception that is distinct from, yet complementary to, the previously characterized CLE19-PXL1-SERK1/2 receptor module. Together, these findings establish a dual-receptor architecture for CLE19 signaling in which BAM3 mediates a transcriptionally distinct branch of the CLE19 pathway. More broadly, this work demonstrates how combinatorial peptide-receptor usage expands the signaling capacity of a single developmental peptide to coordinate robust male reproductive development.