Ploidy and local environment drive intraspecific variation in endoreduplication in Arabidopsis arenosa

Premise Endoreduplication, nonheritable duplication of a nuclear genome, is widespread in plants and plays a role in developmental processes related to cell differentiation. However, neither ecological nor cytological factors influencing intraspecific variation in endoreduplication are fully understood. Methods We cultivated plants covering the range‐wide natural diversity of diploid and tetraploid populations of Arabidopsis arenosa in common conditions to investigate the effect of original ploidy level on endoreduplication. We also raised plants from several foothill and alpine populations from different lineages and of both ploidies to test for the effect of elevation. We determined the endoreduplication level in leaves of young plants by flow cytometry. Using RNA‐seq data available for our populations, we analyzed gene expression analysis in individuals that differed in endoreduplication level. Results We found intraspecific variation in endoreduplication that was mainly driven by the original ploidy level of populations, with significantly higher endoreduplication in diploids. An effect of elevation was also found within each ploidy, yet its direction exhibited rather regional‐specific patterns. Transcriptomic analysis comparing individuals with high vs. low endopolyploidy revealed a majority of differentially expressed genes related to the stress and hormone response and to modifications especially in the cell wall and in chloroplasts. Conclusions Our results support the general assumption of higher potential of low‐ploidy organisms to undergo endoreduplication and suggest that endoreduplication is further integrated within the stress response pathways for a fine‐tune adjustment of the endoreduplication process to their local environment.