Stem cell turnover constrains somatic mutational diversity in plants

Plants continuously generate new organs throughout their lifetime, a process that relies on a small population of stem cells located at the center of the shoot apical meristem (SAM). These cells self-renew and produce descendants that are displaced to the SAM periphery, where they contribute to organ formation and differentiation. Although the population is maintained over time, stochastic or biased turnover can lead to the dominance of specific lineages. Because de novo somatic mutations are inherited along cell lineages, these dynamics are expected to play a central role in shaping the accumulation and distribution of within-plant somatic genetic variation. In this Hypothesis, we discuss the mechanisms underlying stem cell behavior, and hypothesize that stem cell turnover reduces genetic diversity within the SAM over developmental timescales. We also develop a mathematical model linking stem cell turnover to somatic mutation accumulation and predict that this reduction arises because higher turnover limits the co-existence of independent stem cell lineages. Finally, we outline how lineage tracking and somatic DNA sequencing could be used to test these predictions in vivo.