SUMMARY
Because plants do not possess a proper germline, deleterious mutations that occur in the soma can be passed to gametes. It has generally been assumed that the large number of somatic cell divisions separating zygote from gamete formation in long-lived plants should lead to many mutations. However, a recent study showed that surprisingly few cell divisions separate apical stem cells from axillary stem cells in annual plants, challenging this view. To test this prediction, we generated and analysed the full genome sequence of two terminal branches of a 234-year-old oak tree and found very few fixed somatic single-nucleotide variants (SNVs), whose sequential appearance in the tree could reliably be traced back along nested sectors of younger branches. Our data indicate that the stem cells of shoot meristems in trees are robustly protected from accumulation of mutations, analogous to the germline in animals.
