Biology subjects

Figueiredo, D. D.

Publications and source records attributed to Figueiredo, D. D..

6 recordsLinked to original sources

bioRxiv2026

Sex without crossovers mimics clonal reproduction in the holocentric plant Rhynchospora tenuis

Meiotic recombination ensures accurate chromosome segregation and promotes genetic diversity by generating crossovers between homologous chromosomes1. While essential in most sexually reproducing organisms, recombination is variably regulated and can be absent in some lineages, a condition known as achiasmy2. However, obligate achiasmy in both sexes of a sexual species has not been previously documented. Here, we investigate the beak-sedge Rhynchospora tenuis, a holocentric plant with the lowest known chromosome number among flowering plants (n = 2) and inverted meiosis3. Using chromosome-scale genome assemblies from nine accessions, molecular cytogenetics, immunocytochemistry, high-throughput single-gamete sequencing and whole-genome sequencing of controlled crosses, we show that R. tenuis undergoes obligate, genome-wide achiasmy in both male and female meiosis. Despite normal early meiotic axis formation, synapsis fails, crossovers are not detected cytologically or genetically, and univalents persist at metaphase I. Extensive haplotype-specific accumulation of transposable elements (TEs) generates segregation distortion (e.g. meiotic drive), favouring the transmission of larger, TE-rich chromosomes. Remarkably, sexual reproduction is retained with fertilisation producing viable seeds only when translocation-compatible gametes meet, indicating strong post-meiotic selection that eliminates incompatible homozygous combinations. As a result, all surviving offspring are genetically identical to the maternal genotype, effectively restoring heterozygosity each generation and mimicking clonal reproduction. We propose that the combined effects of recombination loss, low chromosome number, holocentricity, inverted meiosis, and selective transmission of longer chromosomes enable faithful segregation and clonal-like inheritance despite sexual reproduction. These findings challenge the boundary between sex and clonality, revealing a unique evolutionary strategy linking genome architecture, recombination loss, and transmission bias.

evolutionary biology↗

bioRxiv2025

An embryo-derived peptide signal directs endosperm polarity in Arabidopsis

Angiosperm seed formation requires the coordinated development of the products of double fertilization, the embryo and the endosperm. The endosperm mediates efficient nutrient transfer from surrounding maternal tissues to the developing embryo. This function requires a polarized tissue organization, which manifests as early polar gene expression and polar cellularization dynamics. We show that the receptor kinase HAIKU2 acts in coordination with the transcription factor WRKY10/MINISEED3 to ensure robust endosperm polarity establishment through the activity of the homeodomain transcription factors WUSCHEL-RELATED HOMEOBOX 8 and 9. This process depends on egg cell fertilization and is mediated through the peptide PATHOGEN-INDUCED PEPTIDE-LIKE 7, which acts as a HAIKU2 ligand. Our results reveal how a molecular paracrine dialogue between the embryo and endosperm ensures optimal seed developmental coordination.

plant biology↗

bioRxiv2024

Genomic imprinting in an early-diverging angiosperm reveals ancient mechanisms for seed initiation in flowering plants

The evolution of the seed habit marks a pivotal innovation of the spermatophytes. Angiosperms further refined this trait by coupling the development of seed accessory structures to fertilization, optimizing resource allocation. Here, we demonstrate that post-fertilization auxin production is an evolutionarily conserved mechanism for seed initiation in angiosperms. We also provide evidence that this pathway likely emerged from a switch from maternal to paternal control after the divergence of angiosperms from their gymnosperm ancestors. Our study thus brings new insights into the evolutionary origins of the endosperm, which was a determining feature for the rapid rise to dominance of flowering plants.

plant biology↗

bioRxiv2023

Seed coat formation in Arabidopsis requires a concerted action of JUMONJI histone H3K27me3 demethylases and Brassinosteroid signaling

Seed development in angiosperms starts with double fertilization, where two paternal sperm cells fertilize the maternal gametes. This leads to the formation of the embryo and of the endosperm. These fertilization products are enveloped by the maternally-derived seed coat, the development of which is inhibited prior to fertilization by the Polycomb Repressive Complex 2 (PRC2). This complex deposits the repressive histone mark H3K27me3, whose removal is necessary for seed coat formation. Here, we show that JUMONJI-type (JMJ) histone demethylases are expressed in the seed coats of Arabidopsis thaliana (Arabidopsis) and are necessary for its formation. We propose that JMJ activity is coupled to Brassinosteroid (BR) function, as BR effectors physically recruit JMJ proteins to target loci. Consistent with this, we show that loss of BR biosynthesis and signaling leads to seed coat defects, and that loss of the main BR receptor, BRI1, results in H3K27me3 hypermethylation. Moreover, our data points to BRI1 mediating H3K27me3 removal independently of BRs, while a different receptor, BRL3, likely regulates seed coat formation in a BR-dependent manner. We thus propose a model where seed coat development relies on canonical and non-canonical functions of BR receptors.

plant biology↗

bioRxiv2023

Comparative transcriptomics of seed nourishing tissues: uncovering conserved and divergent pathways in seed plants

The evolutionary and ecological success of spermatophytes is intrinsically linked to the seed habit, which provides a protective environment for the initial development of the new generation. This environment includes an ephemeral nourishing tissue that supports embryo growth. In gymnosperms this tissue originates from the asexual proliferation of the maternal megagametophyte, while in angiosperms it is a product of fertilization, and is called the endosperm. The emergence of these nourishing tissues is of profound evolutionary value, and they are also food staples for most of the worlds population. Here, using Orthofinder to infer orthologue genes among novel and previously published datasets, we provide a comparative transcriptomic analysis of seed nourishing tissues from representative species of all main angiosperm clades, including those of early diverging basal angiosperms, and a gymnosperm representative. Our results show that, although the structure and composition of seed nourishing tissues has seen significant divergence along evolution, there are signatures that are conserved throughout the phylogeny. Conversely, we identified processes that are specific to species within the clades studied, and thus illustrate their functional divergence. With this, we aimed to provide a foundation for future studies on the evolutionary history of seed nourishing structures, as well as a resource for gene discovery in new functional studies. Significance StatementWithin seeds a specialized structure is responsible for nourishing the embryo during its development. These nourishing tissues are also important sources of staple foods and feed. Here, we provide novel gene expression datasets of nourishing tissues of early diverging angiosperms, and use this information for a meta-analysis to identify pathways conserved, or divergent, throughout evolution. Thus, we aim to provide a resource for gene discovery for seed biology studies.

plant biology↗

bioRxiv2017

Auxin regulates endosperm cellularization in Arabidopsis

The endosperm is an ephemeral tissue that nourishes the developing embryo, similar to the placenta in mammals. In most angiosperms endosperm development starts as a syncytium, where nuclear divisions are not followed by cytokinesis. The timing of endosperm cellularization largely varies between species and the event triggering this transition remains unknown. Here we show that increased auxin biosynthesis in the endosperm prevents its cellularization, leading to seed arrest. Auxin-overproducing seeds phenocopy paternal-excess triploid seeds derived from hybridizations of diploid maternal plants with tetraploid fathers. Concurrently, auxin-related genes are strongly overexpressed in triploid seeds, correlating with increased auxin activity. Reducing auxin biosynthesis and signaling reestablishes endosperm cellularization in triploid seeds and restores their viability, highlighting a causal role of increased auxin in preventing endosperm cellularization. We propose that auxin determines the time of endosperm cellularization and thereby uncovered a central role of auxin in establishing hybridization barriers in plants.

plant biology↗