Hanlon Vincent C T, Otto Sarah P, Aitken Sally N
Faculty of Forestry Department of Forest and Conservation Sciences University of British Columbia Vancouver BC V6T 1Z4 Canada.
Department of Zoology & Biodiversity Research Centre University of British Columbia Vancouver BC V6T 1Z4 Canada.
Evol Lett. 2019 Jun 10;3(4):348-358. doi: 10.1002/evl3.121. eCollection 2019 Aug.
The rates and biological significance of somatic mutations have long been a subject of debate. Somatic mutations in plants are expected to accumulate with vegetative growth and time, yet rates of somatic mutations are unknown for conifers, which can reach exceptional sizes and ages. We investigated somatic mutation rates in the conifer Sitka spruce ( (Bong.) Carr.) by analyzing a total of 276 Gb of nuclear DNA from the tops and bottoms of 20 old-growth trees averaging 76 m in height. We estimate a somatic base substitution rate of 2.7 × 10 per base pair within a generation. To date, this is one of the highest estimated per-generation rates of mutation among eukaryotes, indicating that somatic mutations contribute substantially to the total per-generation mutation rate in conifers. Nevertheless, as the sampled trees are centuries old, the per-year rate is low in comparison with nontree taxa. We argue that although somatic mutations raise genetic load in conifers, they generate important genetic variation and enable selection both among cell lineages within individual trees and among offspring.
体细胞突变的速率及其生物学意义长期以来一直是一个争论的话题。植物中的体细胞突变预计会随着营养生长和时间的推移而积累，然而，对于可以长得非常高大且寿命很长的针叶树来说，体细胞突变的速率尚不清楚。我们通过分析来自20棵平均高度为76米的老龄树木顶部和底部的总共276Gb核DNA，研究了针叶树西加云杉（(Bong.) Carr.）的体细胞突变率。我们估计在一代中体细胞碱基替换率为每碱基对2.7×10 。迄今为止，这是真核生物中估计的每代最高突变率之一，表明体细胞突变对针叶树每代的总突变率有很大贡献。然而，由于采样的树木已有数百年历史，与非树木类群相比，每年的突变率较低。我们认为，尽管体细胞突变会增加针叶树的遗传负荷，但它们会产生重要的遗传变异，并使个体树木内的细胞谱系之间以及后代之间都能进行选择。
