Crhak Khaitova, L. | Search bioRxiv

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↗

bioRxiv2023

Heat stress impairs centromere structure and segregation of meiotic chromosomes in Arabidopsis

Heat stress is a major threat to global crop production, and understanding its impact on plant fertility is crucial for developing climate-resilient crops. Despite the known negative effects of heat stress on plant reproduction, the underlying molecular mechanisms remain poorly understood. Here, we investigated the impact of elevated temperature on centromere structure and chromosome segregation during meiosis in Arabidopsis thaliana. Consistent with previous studies, heat stress leads to a decline in fertility and micronuclei formation in pollen mother cells. Our results reveal that elevated temperature causes a decrease in the amount of centromeric histone and the kinetochore protein BMF1 at meiotic centromeres with increasing temperature. Furthermore, we show that heat stress increases the duration of meiotic divisions and prolongs the activity of the spindle assembly checkpoint during meiosis I, indicating an impaired efficiency of the kinetochore attachments to spindle microtubules. Our analysis of mutants with reduced levels of centromeric histone suggests that weakened centromeres sensitize plants to elevated temperature, resulting in meiotic defects and reduced fertility even at moderate temperatures. These results indicate that the structure and functionality of meiotic centromeres in Arabidopsis are highly sensitive to heat stress, and suggest that centromeres and kinetochores may represent a critical bottleneck in plant adaptation to increasing temperatures.

plant biology↗