The recruitment of the A-type cyclin TAM to stress granules is crucial for meiotic fidelity under heat

Stress granules (SG) are biomolecular condensates that represent an adaptive response of cells to various stresses, including heat. However, the cell type-specific function and relevance of SG formation, especially during reproductive development, are largely not understood. Here, we show that the meiotic A-type cyclin TARDY ASYNCHRONOUS MEIOSIS (TAM) is recruited to SGs in male meiocytes of <i>Arabidopsis</i> after exposure to heat. We find that the amino terminus of TAM is necessary and sufficient for the localization of proteins to meiotic SGs. Swapping the amino terminus of TAM with the one of its sister protein CYCA1;1 resulted in a separation-of-function allele of <i>TAM</i>, which prevents the partitioning of TAM to SGs while restoring a wild-type phenotype in a <i>tam</i> mutant background under nonheat stress conditions. Notably, plants expressing this <i>TAM</i> version prematurely terminate meiosis under heat resulting in unreduced gametes. Thus, the formation of TAM-containing SGs is necessary for genome stability under heat stress.