Biology subjects

Giraldo-Fonseca, A.

Publications and source records attributed to Giraldo-Fonseca, A..

4 recordsLinked to original sources

bioRxiv2026

H3K4me3 recruits the chromatin remodeling DILL-PICKLE-PEPPERCORN complexes to promoters in plants

The plant CHD chromatin remodeler PICKLE (PKL) is a master regulator of cellular identity and differentiation, controlling developmental, hormonal and stress-response processes. Yet the molecular mechanisms underlying its function remain unclear. Here, we show that PKL forms three complexes, each composed of a protein of previously unknown function and one of three mutually exclusive novel DNAJ proteins that recruit HSP70-1. Simultaneous loss of all three DNAJs phenocopies the pkl mutant, indicating functional redundancy among PKL complexes. In vitro activity assays and cryo-electron microscopy reveal that PKL clamps nucleosomal DNA via its ATPase motor domain and recognizes H3K4me3 through its double chromodomain. Genome-wide profiling shows that H3K4me3 recognition positions PKL complexes at genic promoters to bidirectionally fine-tune gene expression. Together, these results provide structure-function insight into PKL recruitment and its control of developmental gene expression, and reveal a chaperone-coupled complex assembly that offers a broader perspective on how chaperone networks may support chromatin remodeling complexes across eukaryotes.

plant biology↗

bioRxiv2025

A citrullination-ubiquitination pathway controls pre-meiotic H1 eviction and is essential for gametogenesis in Arabidopsis

Despite being evolutionary distant, plants and animals share a common phenomenon at the somatic-to-reproductive cell fate transition with extensive structural and compositional changes in chromatin. Such chromatin reprogramming occurs in the plant SMCs (Spore Mother Cells) and animal PGCs (primordial germ cells) and is initiated by the loss of linker histones (H1). H1 loss is essential to establish pluripotency in animal PGCs but its role is not known in plants. Here, we identified two regulatory pathways involving a citrullinase and an E3-ubiquitin ligase that contribute H1.1 loss in female SMC in Arabidopsis. We also identified roles for two specific residues: an arginine, whose positive charge contributes to H1.1 destabilization from chromatin, and a lysine in the globular domain that is essential for H1.1 degradation. Ovules with impaired H1.1 loss in the SMC proceed through sporogenesis but fail to complete gametogenesis. We propose a citrullination-ubiquitination pathway governing pre-meiotic H1 depletion as a critical mechanism for establishing post-meiotic competence in the Arabidopsis germline.

plant biology↗

bioRxiv2020

Characterization of the single FERONIA homolog in Marchantia polymorpha reveals an ancestral role of CrRLK1L receptor kinases in regulating cell expansion and morphological integrity

Plant cells are surrounded by a cell wall, a rigid structure that is not only important for cell and organ shape, but crucial for intercellular communication and interactions with the environment. In the flowering plant Arabidopsis thaliana, the 17 members of the Catharanthus roseus RLK1-like (CrRLK1L) receptor kinase family are involved in a multitude of physiological and developmental processes, making it difficult to assess their primary or ancestral function. To reduce genetic complexity, we characterized the single CrRLK1L gene of Marchantia polymorpha, MpFERONIA (MpFER). Plants with reduced MpFER levels show defects in vegetative development, i.e., rhizoid formation and cell expansion, and have reduced male fertility. In contrast, Mpfer null mutants and overexpression lines severely affect cell integrity and morphogenesis of the gametophyte. Thus, the CrRLK1L gene family originated from a single gene with an ancestral function in cell expansion and the maintenance of cellular integrity. During land plant evolution, this ancestral gene diversified to fulfil a multitude of specialized physiological and developmental and roles in the formation of both gametophytic and sporophytic structures essential to the life cycle of flowering plants. Summary statementThe CrRLK1L family arose in land plants and the Marchantia polymorpha genome contains a single copy, MpFER, which is broadly expressed and regulates cell expansion and cell wall integrity.

evolutionary biology↗

bioRxiv2020

Developmental constraints modulate reproductive fate and plasticity within the Arabidopsis ovule primordium

In multicellular organisms, sexual reproduction requires the separation of the germline from the soma. In flowering plants, the first cells of the germline, so-called spore mother cells (SMCs), differentiate as the reproductive organs form. Here, we explored how organ growth influences and contributes to SMC differentiation. We generated a collection of 92 annotated 3D images capturing ovule primordium ontogeny at cellular resolution in Arabidopsis. We identified a spatio-temporal pattern of cell divisions that acts in a domain-specific manner as the primordium forms, which is coupled with the emergence of a single SMC. Using tissue growth models, we uncovered plausible morphogenetic principles involving a spatially confined growth signal, differential mechanical properties, and cell growth anisotropy. Our analysis also reveals that SMC characteristics first arise in more than one cell but SMC fate becomes progressively restricted to a single cell during organ growth. Altered primordium geometry coincided with a delay in this fate restriction process in katanin mutants. Altogether, our study suggests that tissue geometry canalizes and modulates reproductive cell fate in the Arabidopsis ovule primordium.

plant biology↗