Biology subjects

Capitao, C.

Publications and source records attributed to Capitao, C..

4 recordsLinked to original sources

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↗

bioRxiv2022

A complex role of Arabidopsis CDKD;3 in meiotic progression and cytokinesis

Meiosis is a specialized cell division that halves the number of chromosomes in two consecutive rounds of chromosome segregation. In angiosperm plants is meiosis followed by mitotic divisions to form rudimentary haploid gametophytes. In Arabidopsis, termination of meiosis and transition to gametophytic development is governed by TDM1 and SMG7 that mediate inhibition of translation. Mutants deficient in this mechanism do not form tetrads, but instead undergo multiple cycles of aberrant nuclear divisions, that are likely caused by the failure to downregulate cyclin dependent kinases during meiotic exit. A suppressor screen to identify genes that contribute to meiotic exit uncovered a mutation in CDKD;3 that alleviates meiotic defects in smg7 deficient plants. The CDKD;3 deficiency prevents aberrant meiotic divisions observed in smg7 mutants, or delays their onset after initiation of cytokinesis, which permits formation of functional microspores. Although CDKD;3 acts as an activator of CDKA;1, the main cyclin dependent kinase that regulates meiosis, cdkd;3 mutation appears to promote meiotic exit independently of CDKA;1. Furthermore, analysis of CDKD;3 interactome revealed enrichment for proteins implicated in cytokinesis suggesting a more complex function of CDKD;3 in cell cycle regulation.

plant biology↗

bioRxiv2021

A CENH3 mutation promotes meiotic exit and restores fertility in SMG7-deficient Arabidopsis

Meiosis in angiosperm plants is followed by mitotic divisions to form multicellular haploid gametophytes. Termination of meiosis and transition to gametophytic development is, in Arabidopsis, governed by a dedicated mechanism that involves SMG7 and TDM1 proteins. Mutants carrying the smg7-6 allele are semi-fertile due to reduced pollen production. We found that instead of forming tetrads, smg7-6 pollen mother cells undergo multiple rounds of chromosome condensation and spindle assembly at the end of meiosis, resembling aberrant attempts to undergo additional meiotic divisions. A suppressor screen uncovered a mutation in centromeric histone H3 (CENH3) that increased fertility and promoted meiotic exit in smg7-6 plants. The mutation led to inefficient splicing of the CENH3 mRNA and a substantial decrease of CENH3, resulting in smaller centromeres. The reduced level of CENH3 delayed formation of the mitotic spindle but did not have an apparent effect on plant growth and development. We suggest that impaired spindle re-assembly at the end of meiosis limits aberrant divisions in smg7-6 plants and promotes formation of tetrads and viable pollen. Furthermore, the reduced level of CENH3 did not induce haploid plants in crosses with wild plants, indicating that differences in centromere size is not the key determinant of centromere-mediate genome elimination.

genetics↗