Rapid chromosome movements persist within nuclear protrusions in Arabidopsis thaliana meiocytes

Chromosome movements during meiosis are essential for accurate homolog recognition and segregation. However, two striking phenomena, rapid prophase chromosome movements (RPMs) and the formation of unusual nuclear structures, both involving large-scale chromatin dynamics and occurring simultaneously during early meiotic prophase I, remain poorly understood in plants. RPMs are known to facilitate homolog pairing across diverse taxa, but their regulation and robustness in plants remain unclear. Similarly, a phenomenon characterized by the formation of nuclear protrusions, that extend through intercellular channels into the cytoplasm of neighboring meiocytes, is frequently reported during plant meiosis. As a rule, this process is referred to as cytomixis, yet its nature and biological significance remain unresolved. Here, we integrate the study of these processes by investigating Arabidopsis thaliana male meiocytes at early prophase I using live-cell imaging with ASY1:GFP as a reporter for chromosome dynamics. We show that chromatin in nuclear protrusions remains active and displays RPMs indistinguishable from those of intact nuclei. Remarkably, a process unavoidably involving mechanical stress and disruption of cytoskeletal connections, does not interrupt RPMs. These findings demonstrate that meiotic RPMs are inherently robust and largely independent of the local cytoplasmic environment and support the view that cytomixis is a normal cytological process rather than a pathology or artifact.