Biology subjects

Vargova, A.

Publications and source records attributed to Vargova, A..

4 recordsLinked to original sources

bioRxiv2026

A Cajal body assembly factor regulates cell fate transitions in Arabidopsis

Ribonucleoprotein (RNP) condensates are emerging as key regulators of cell fate transitions, yet their functions have been largely linked to mRNA storage and translational control. Here, we uncover a role for Cajal body (CB)-mediated pre-mRNA splicing in coordinating the transition from stem cell divisions to differentiation in plants. We identify THREE-DIVISION MUTANT 3 (TDM3) as a cell cycle-regulated factor required for post-mitotic CB assembly. Loss of TDM3 or the CB scaffold protein COILIN delays differentiation and prolongs formative cell divisions. Transcriptome analysis revealed that TDM3 and COILIN jointly regulate pre-mRNA splicing, including transcripts controlling cell cycle and fate transitions. These findings establish CB-mediated splicing as a mechanism linking cell cycle progression to cellular differentiation.

cell biology↗

bioRxiv2026

MO25 binds CBL-interacting protein kinases associated with ribonucleoprotein condensates and regulates meiotic exit

Meiotic (M)-bodies are multiphasic ribonucleoprotein (RNP) condensates composed of a P-body core surrounded by a stress granule-like shell that promote meiotic exit through transient translational repression. This process depends on the phosphoserine-binding protein SMG7, which recruits the meiotic regulator TDM1 to M-bodies during meiosis II. Here, we identify the evolutionarily conserved scaffold protein MO25 as a regulator of SMG7 and TDM1 partitioning into M-bodies in Arabidopsis thaliana. Disruption of MO25A1 enhances the accumulation of SMG7 and TDM1 in M-bodies and increases the reduced fertility in the hypomorphic smg7-6 mutant, which exhibits impaired M-body association. In fungi and animals, MO25 proteins act as allosteric activators of STE20-family kinases. Interaction screening revealed that, whereas Arabidopsis MO25B proteins interact with STE20-family MAP4K kinases, MO25A paralogues have evolved specificity toward a subset of CBL-interacting protein kinases (CIPKs). Notably, the MO25A-interacting CIPKs localize to diverse nuclear and cytoplasmic RNP condensates. Among them, CIPK6 is required for fertility and pollen development, and disruption of its MO25-binding domain enhances SMG7 condensation. Together, our findings identify a previously unrecognized MO25A-CIPK interaction module that regulates M-body organization and may more broadly contribute to the regulation of RNP condensates.

plant biology↗

bioRxiv2025

Post-transcriptional regulation of meiotic transcripts by the RNA binding protein CDM1 is associated with cytoplasmic condensate assemblies

The transition from diploid to haploid life phases requires extensive reprogramming of gene expression that drive meiotic cell division and the differentiation of haploid forms. A hallmark of meiosis is widespread post-transcriptional regulation, including delayed translation that ensures timely protein production at specific stages. Here, we identify a mechanism controlling the translation of meiotic transcripts in Arabidopsis pollen mother cells, mediated by CALLOSE DEFECTIVE MICROSPORES1 (CDM1). We show that CDM1 affects several meiotic processes, including chromosome pairing, condensation, and cytokinesis. CDM1 forms dynamic, meiosis specific cytoplasmic foci that associate with components of processing bodies and stress granules, giving rise to three-phase condensate assemblies. Biochemical and cellular analyses reveal that CDM1 is an RNA-binding protein with an intrinsic ability to form ribonucleoprotein condensates. Furthermore, we demonstrate that CDM1 binds mRNAs expressed in prophase I and represses their translation until later meiotic stages, coinciding with the disassembly of CDM1 condensates. These findings establish CDM1 as a key post-transcriptional regulator that fine-tunes the expression of meiotic genes to ensure proper progression of microsporogenesis.

plant biology↗

bioRxiv2025

SMG7 and eIF4A constitute a homeostatic module controlling P-body condensation and function of Meiotic bodies

Processing bodies (P-bodies) are ribonucleoprotein condensates that regulate RNA processing and storage. Although present constitutively in most cells, their size and composition dynamically change in response to developmental and environmental cues. However, mechanisms governing P-body assembly and remodelling remain poorly understood. Here we show that in Arabidopsis, SMG7 interacts with the eIF4A helicases and recruits them to P-bodies. eIF4As limit P-bodies condensation and also restrict stress granule (SG) formation under heat stress. We further identify meiotic (M-)bodies as composite RNP granules with a P-body core surrounded by a SG-like shell. The SMG7-eIF4A module regulates the recruitment of the meiosis-specific protein TDM1 into M-bodies, influencing meiotic exit and plant reproduction. Our findings suggest that SMG7 functions as an adaptor protein that recruits client proteins into P-bodies and, together with eIF4A, forms a regulatory module that regulates P-body composition and maintains their size homeostasis.

cell biology↗