Biology subjects

Lafon Placette, C.

Publications and source records attributed to Lafon Placette, C..

6 recordsLinked to original sources

bioRxiv2026

Temporal genomic imprinting regulates grain filling in barley

In cereals, the persistent endosperm accumulates starch and storage proteins, making their grains a major source of food and feed. Early grain development is epigenetically controlled through the parent-of-origin-specific expression of imprinted genes in the endosperm that regulate endosperm proliferation, nutrient accumulation and embryo nourishment. Imprinted genes have been identified in several major cereals, and a few have been functionally characterized. However, it is unclear how imprinted genes regulate the accumulation of storage compounds in cereal grains. Through spatiotemporal transcriptome analysis of 255 imprinted genes in barley (Hordeum vulgare), we identify endosperm transfer cells in grains as a hotspot of expression of imprinted genes. Furthermore, we show that transcription factor LYS3 dynamically regulates grain filling in barley through early expression of the maternal allele, followed by partial activation of the paternal allele.

plant biology↗

bioRxiv2026

Imprinted regulatory networks reveal the molecular cross-talk between paternal and maternal genomes in the endosperm of Arabidopsis arenosa

Summary paragraphImprinted genes do not act alone to shape seed development, but as a complex network -- just like any other gene. Yet, the molecular context in which they are embedded, i.e. their gene network, remains largely understudied. To address this knowledge gap, we characterized the imprintome of Arabidopsis arenosa at the species-level and used gene regulatory network analyses. We show that genomic imprinting preferentially affects only a few pathways, offering candidates for dosage sensitive processes and the molecular arena of parental conflict. In these pathways, some imprinted genes act as hub genes, among which NRPE1, highlighting the importance of epigenetics in endosperm development. The interaction between parental genomes was rather one-sided: paternally expressed regulators preferentially targeted PEGs, while maternally expressed regulators targeted both PEGs and MEGs indiscriminately. This aligns with a self-promoting paternal influence and a maternal buffer under a parental conflict scenario. Shared paternal and maternal regulation of downstream targets was nevertheless common, and we reveal novel molecular interactions between imprinted regulators. Overall, our work shows how genomic imprinting may act as a molecular means for parental conflict, but also highlights the importance of parental molecular coordination in endosperm development.

plant biology↗

bioRxiv2026

Transcriptomic insights into triploid seed failure in Arabidopsis arenosa natural populations

O_LIPolyploidy is a key evolutionary force in plants; among its many consequences, hybridization between diploids and polyploids is restricted due to the "triploid block". While the molecular mechanisms of this postzygotic barrier are extensively studied in the model species Arabidopsis thaliana, our understanding of the triploid block in natural systems remains limited. C_LIO_LIHere, we investigated the transcriptome of failing triploid seeds in Arabidopsis arenosa, a close relative of A. thaliana with diploid and autotetraploid populations meeting in nature. We also identified A. arenosa imprinted genes. C_LIO_LITriploid seeds showed preferential misregulation of imprinted genes, which parallels the parent-of-origin features of the triploid block. Tissue-specific transcriptomic analyses revealed pathogen defense-like response being recurrently affected in the endosperm and seed coat. This pathway is commonly misregulated in all species with triploid seed transcriptomes studied to date. The associated genes however are likely more involved in cell-cell signaling rather than pathogen defense per se. C_LIO_LIAltogether, this study depicts a thorough molecular landscape of the triploid block for the first time in natural systems. Combining data on the understudied maternal excess transcriptome, a new imprintome, a tissue-specific focus, and a cross-species comparison, this study also advances our understanding of the triploid block and seed development. C_LI

evolutionary biology↗

bioRxiv2024

The effect of parental conflict in imprinting genes in A. lyrata.

Genomic imprinting is a form of gene regulation leading to the unequal expression of maternal and paternal alleles. The main hypothesis invoked to explain the evolution of imprinted genes is the kinship theory, which posits a conflict between parental genomes over resource allocation in progeny. According to this theory, such conflicts select for parent-of-origin-dependent expression of genes involved in resource allocation. How such conflicts translate into signatures of selection at coding or regulatory sequences remains model-dependent and is not explicitly predicted by the kinship theory. However, most studies addressing selection in imprinted genes in flowering plants, particularly those based on population-genomic or phylogenetic analyses, have focused on self-fertilizing species, where conflicts over resource allocation are predicted to be weak. Consequently, the impact of the kinship theory on the evolution of imprinted genes remains largely unexplored in systems where parental conflict is expected to be strong. Furthermore, potential coevolution between antagonistically acting imprinted genes, as proposed in extensions of parental conflict models, has not yet been tested empirically. Using combined phylogenetic and population genomic approaches, we investigated signatures of selection on imprinted genes across the Brassicaceae family and in autogamous and allogamous populations of Arabidopsis lyrata, and searched for evidence of coevolution among imprinted genes. We found that endosperm-expressed genes exhibited signals of balancing selection across Brassicaceae and within allogamous populations, consistent with models of unresolved intralocus conflict. These population-level signals varied with the mating system, in line with expectations that parental conflict is reduced under self-fertilization. Moreover, phylogenetic analyses indicated signatures of purifying (negative) selection acting on imprinted genes. However, the population-level signatures of selection were independent of the mating system and showed limited concordance with kinship predictions, possibly due to stronger selection acting on expression than on coding sequences. Finally, we identified coevolution between imprinted genes, although not at specific sites, suggesting that interactions beyond protein sequence may contribute to this process.

evolutionary biology↗

bioRxiv2024

Varying importance of postzygotic isolation in polyploid speciation? A survey of the triploid block strength, its causal mechanisms, and evolutionary consequences

The triploid block, primarily caused by endosperm developmental issues, is known as a significant barrier to interploidy hybridization among flowering plants and thereby, polyploid speciation. However, its strength varies across taxa, with some instances of leakiness, questioning its universal role as a barrier. We conducted a literature survey to explore the causes of the variation in the strength of triploid block across angiosperms. We particularly assessed the impact of interploidy cross direction, types of endosperm development, endosperm persistence at seed maturity, and ploidy divergence. None of these factors had a significant impact on triploid seed viability, likely due to limited data and inconsistencies in estimation methods across the literature. In addition, triploid seed viability in experimental crosses was sometimes correlated to the occurrence of triploid hybrids in nature, sometimes not, suggesting a mixed role of the triploid block in shaping interspecies gene flow. Altogether, our study highlights the need for unified approaches in future studies on the triploid block to advance our understanding of its variation and evolutionary implications.

evolutionary biology↗

bioRxiv2020

Hybrid seed incompatibility in Capsella is connected to chromatin condensation defects in the endosperm

Hybridization of closely related plant species is frequently connected to endosperm arrest and seed failure, for reasons that remain to be identified. In this study, we investigated the molecular events accompanying seed failure in hybrids of the closely related species pair Capsella rubella and C. grandiflora. Mapping of QTLs for the underlying cause of hybrid incompatibility in Capsella revealed three QTLs that were close to pericentromeric regions. This prompted us to investigate whether there are specific changes in heterochromatin associated with interspecific hybridizations. Indeed, we found that chromatin was less condensed in the endosperm, while the embryo was not affected. Loss of chromosome condensation was connected with a strong loss of CHG and CHH methylation and mitotic abnormalities. Genome-wide sequencing of hybrid endosperm revealed that the chromosome loss was random and was likely a consequence of reduced chromatin condensation. Consistent with reduced DNA methylation in hybrid endosperm, we found a disproportionate deregulation of genes located close to pericentromeric regions. Among those deregulated genes there were many potential targets of the AGAMOUS-LIKE transcription factor PHERES1, suggesting that reduced DNA methylation allows PHERES1 to hyperactivate its targets. Since the identified QTLs were also associated with pericentromeric regions, we conclude that relaxation of heterochromatin in response to interspecies hybridization exposes and activates loci leading to hybrid seed failure.

evolutionary biology↗