This work demonstrates how combinatorial peptide-receptor usage expands the signaling capacity of a single developmental peptide to coordinate robust male reproductive development.
Abstract
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.
Sharing the most recent common ancestor, receptor-like kinases EXCESS MICROSPOROCYTES1 (EMS1) and BRASSINOSTEROID INSENSITIVE1 (BRI1) family members respectively perceive the peptide ligand TAPETUM DETERMINANT1 (TPD1) and the phytohormone brassinosteroids (BRs) to activate the same downstream BRI1 EMS SUPPRESSOR1 (BES1)/BRASSINAZOLE RESISTANT1 (BZR1) transcription factor family. Yet only their distinct canonical functions have been revealed. TPD1 specifically sustains tapetum development but is dispensable for global plant growth, whereas BRs regulate overall plant growth without impacting tapetum development. This generates a fundamental evolutionary conflict: gradual biochemical divergence with saltational biological diversification. Here, we identify an unrecognized redundant role of TPD1 and BR signaling in controlling early anther lobe formation. Simultaneous disruption of both pathways causes a lobeless anther defect, phenocopying the loss of the entire BES1/BZR1 family. Single-pathway disruption produces no such defect. Interestingly, we found that pathway specificity during tapetum development is caused by spatiotemporal ligand dynamics. The expression of DWF4 (encoding a rate-limiting BR biosynthetic enzyme) decreases sharply at the onset of tapetum development, while TPD1 expression remains stable. Consistently, exogenous BR application or the introduction of an active, ligand-independent BRI1 rescues tapetum defects in either the ems1 mutant or the dual-pathway-deficient mutant background. Our findings reconcile biochemical divergence and biological diversification with gradual evolution, likely stimulating study of the functional divergence of numerous other receptor-like kinases at multiple levels.
Weiyue Chen, Li-Ming He, Jingjie Zhang et al.· Current Biology· 0 citations
Anther tapetum degradation is essential for normal pollen formation in rice, yet the underlying regulatory network remains poorly understood. We isolated a novel male sterility rice mutant, osglox5, and confirmed that the target gene LOC_Os11g06870 encodes a glyoxal/galactose oxidase protein with both glyoxal oxidase (GLOX) and galactose oxidase (GAO) activities and is required for hydrogen peroxide (H2O2) production in anthers. Insufficient H2O2 content in osglox5 anthers causes delayed tapetum degradation and defective pollen wall formation, resulting in pollen abortion. OsGLOX5 is highly expressed during stage 9 of anther development, specifically in microspores and tapetum, and localizes to the endoplasmic reticulum. The tapetum-specific transcription factor OsMYB103 directly binds the OsGLOX5 promoter and activates its expression. This study provides the first evidence that a protein with both glyoxal oxidase and galactose oxidase activities plays an essential role in rice tapetum degradation, and identifies a novel MYBs-GLOXs regulatory axis, advancing our understanding of the tapetum degradation network.
Weichi Liu, Jie Yang, Yuanlin Chen et al.· Plant Physiology· 0 citations
Plant growth and reproduction require coordinated control of hormone-dependent tissue patterning and faithful meiotic chromosome segregation, yet whether upstream proteostasis contributes to both processes remains unclear. Here, we show that Arabidopsis PROTEIN DISULFIDE ISOMERASE 5 (PDI5) contributes to auxin-associated developmental patterning and meiotic fidelity. Native-promoter reporter constructs corresponding to two annotated PDI5 transcript isoforms show distinct subcellular enrichment, with one displaying an endoplasmic reticulum (ER)-associated distribution and the other showing nuclear enrichment. Disruption of PDI5 alters bulk glycoprotein staining and glycoside and trafficking-associated transcriptional programs, reduces the abundance of PIN-FORMED 2-green fluorescent protein (PIN2-GFP), alters its brefeldin A-sensitive intracellular accumulation, and is associated with perturbed auxin-response patterning and disorganized root meristems. In reproductive tissues, the pdi5 mutant shows abnormal germline-associated cell-fate restriction, impaired meiotic chromosome behavior, reduced chiasma formation and decreased fertility. Proteomic and interaction analyses identify the cohesin subunit SISTER-CHROMATID COHESION PROTEIN 3 (SCC3) as a PDI5-associated protein, and disruption of a conserved SCC3 N809-centered motif reduces its detectable association with PDI5. In a PDI5 promoter-driven conditional complementation assay, SCC3^N809E fails to support fertility rescue. These findings support a model in which PDI5-dependent proteostasis contributes to auxin-associated developmental patterning and meiotic chromosome fidelity, potentially through compartmentally distributed PDI5 functions.
M. Aslam, Beenish Fakher, B. H. Jakada et al.· New Phytologist· 0 citations
A WRKY-MYB cascade that mediates SCW formation in H. brasiliensis is revealed, extending the classical NAC-MYB regulatory framework and providing molecular targets for improving xylem properties and stress resilience in tropical perennial crops.
Jinjing Pan, Yanhong Xu, Junchao Zhao et al.· Plant, Cell and Environment· 0 citations
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.
An Luo, Ying Qiao, Siyuan Li et al.· Plant and Cell Physiology· 0 citations
The pistil, a key female reproductive organ in flowering plants, plays a critical role in sexual reproduction. Although pistil function has been well studied in some species, the molecular mechanisms governing its development in rice (Oryza sativa) remain unclear. Here, we isolated and characterized a female-sterile rice mutant, Osdpms1, that exhibits pleiotropic reproductive defects, including greater stigma number and aberrant gametophyte development, while maintaining normal vegetative growth and male fertility. Using map-based cloning, genetic complementation, and CRISPR-Cas9 knockout experiments, we determined that LOC_Os07g03160 (named OsDPMS1), encoding a protein containing a WD40 repeat domain, is the causal gene underlying the mutant phenotype. OsDPMS1 was predominantly expressed during the flowering stage, and subcellular localization experiments revealed that OsDPMS1 localizes to both the nucleus and the cytoplasm. Using yeast two-hybrid, bimolecular fluorescence complementation, and GST-pulldown assays, we demonstrated that OsDPMS1 physically interacts with three components of the 26S proteasome pathway: OsUBQ, OsCDC48, and OsCDC48E. Furthermore, we showed that the female sterility of Osdpms1 can be efficiently maintained via seed production technology. When we combined Osdpms1 with male-sterile lines for hybrid seed production in a mixed planting manner, we achieved yield potentials comparable to those using conventional row-planting methods. Our findings establish OsDPMS1 as a critical regulator of pistil development and female fertility in rice and highlight its potential application in hybrid rice breeding programs.