Patterns of Stem Cell Divisions Contribute to Plant Longevity
Patterns of Stem Cell Divisions Contribute to Plant Longevity
复制标题
DOI：
10.1016/j.cub.2016.03.067
复制
发表时间：
2016-06-06
期刊：
影响因子：
9.2
通讯作者：
Kuhlemeier, Cris
中科院分区：
文献类型：
--
作者：
Burian, Agata;de Reuille, Pierre Barbier;Kuhlemeier, Cris
植物的寿命从一年几周到树上几千年不等。考虑到DNA复制错误不可避免地会导致突变，很难解释如此长寿的原因。如果不通过减数分裂重组进行净化，体细胞突变的积累最终将导致突变的崩溃，这种现象被称为穆勒棘轮。然而，树木的寿命更多地受到偶发疾病或结构破坏的限制，而不是遗传老化。树结构的关键决定因素是腋生分生组织，它在树叶的腋下形成，并向外生长形成枝条。一年生植物的分枝数量较少，但在多年生植物中，重复分枝可以导致数千个顶生分枝。在这里，我们使用干细胞消融和定量细胞谱系分析来表明腋生分生组织很早就被搁置了，类似于后生动物生殖系。当相邻细胞分裂旺盛时，腋生分生组织前体保持静止状态，顶端和腋生分生组织之间只有7-9个细胞分裂。在迭代分支过程中，分支的数量呈指数增加，而细胞分裂的数量呈线性增加。此外，计算模型表明，干细胞的排列和腋生分生组织的定位分布在主芽周围的体细胞突变，阻止了它们的固定，并最大化了遗传异质性。这些特点减慢了穆勒的棘轮速度，从而延长了寿命。
The lifespan of plants ranges from a few weeks in annuals to thousands of years in trees. It is hard to explain such extreme longevity considering that DNA replication errors inevitably cause mutations. Without purging through meiotic recombination, the accumulation of somatic mutations will eventually result in mutational meltdown, a phenomenon known as Muller's ratchet. Nevertheless, the lifespan of trees is limited more often by incidental disease or structural damage than by genetic aging. The key determinants of tree architecture are the axillary meristems, which form in the axils of leaves and grow out to form branches. The number of branches is low in annual plants, but in perennial plants iterative branching can result in thousands of terminal branches. Here, we use stem cell ablation and quantitative cell-lineage analysis to show that axillary meristems are set aside early, analogous to the metazoan germline. While neighboring cells divide vigorously, axillary meristem precursors maintain a quiescent state, with only 7-9 cell divisions occurring between the apical and axillary meristem. During iterative branching, the number of branches increases exponentially, while the number of cell divisions increases linearly. Moreover, computational modeling shows that stem cell arrangement and positioning of axillary meristems distribute somatic mutations around the main shoot, preventing their fixation and maximizing genetic heterogeneity. These features slow down Muller's ratchet and thereby extend lifespan.