Geelen, D. N. V. | bioRxiv Science

bioRxiv2024

Ultraviolet attenuates centromere-mediated meiotic genome stability and alters gametophytic ploidy consistency in flowering plants

Ultraviolet (UV) radiation influences development and genome stability in organisms; however, its impacts on meiosis, a special cell division essential for the delivery of genetic information over generations in eukaryotes, remain not yet elucidated. In this study, we demonstrate that UV attenuates the centromere-mediated meiotic chromosome stability and induces unreduced gametes in Arabidopsis thaliana. We show that UV reduces crossover (CO) rate but does not interfere with meiotic chromosome integrity. Functional centromere-specific histone 3 (CENH3) is required for the obligate CO formation, and plays a role in protection of homolog synapsis and sister-chromatid cohesion under UV stress. Moreover, UV specifically alters the orientation and organization of spindles and phragmoplasts at meiosis II, resulting in meiotic restitution and unreduced gametes. Further, we determine that UV-induced meiotic restitution does not rely on the UV Resistance Locus8-mediated UV perception and the Tapetal Development and Function1- and Aborted Microspores-dependent tapetum development, but occurs possibly via impacted JASON function and downregulated Parallel Spindle1. This study sheds light on the impacts of UV on meiotic genome stability and gametophytic ploidy consistency, which thus may influence genome evolution in flowering plants.

plant biology↗

bioRxiv2022

Heat induced male meiotic restitution and sexual polyploidisation through natural variation of the Arabidopsis cyclin TAM/CYCA1;2

Heat stress promotes the formation of unreduced (2n) male gametes through meiotic restitution, a driving force of evolutionary polyploidisation. Here we report that the molecular mechanism underlying heat tolerance of the meiotic division program in Arabidopsis thaliana relies on sustained protein translation of cell cycle genes. By leveraging natural variation in the Arabidopsis population, we identified heat-sensitive and heat-tolerant alleles of TARDY ASYNCHRONOUS MEIOSIS/CYCLINA1;2 (TAM). We show that TAM associates with specialised biomolecular condensates in meiotic cells under high temperatures. Through a mechanism that involves THREE DIVISION MUTANT1 (TDM1), TAM is required to maintain the translation of key meiotic cell cycle genes, including its own, thus preventing premature meiotic exit under heat stress conditions. Boosting TAM translation in heat-sensitive accessions using complementary peptides is sufficient to rescue the heat-induced defects. We propose that this mechanism can play a role in polyploidisation events and plant evolution in the context of the ongoing global climate change.

plant biology↗