Couturier Étienne, Llanos Paula, Lizée Antoine, Besson Sébastien, Dumais Jacques
Université Paris-Diderot, Paris, France.
Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Viña del Mar, Chile.
Am J Bot. 2025 Apr;112(4):e70027. doi: 10.1002/ajb2.70027. Epub 2025 Apr 4.
Apical meristems of land plants have played a fundamental role in the evolution of complex shoot architectures. The most common structure of shoot apical meristems in bryophytes, lycophytes, and ferns is characterized by a single apical cell surrounded by a spiral of apical derivatives. Despite the importance of this type of meristem organization, it remains unclear how it is maintained at the apex.
We analyzed the distribution of different meristem organizations within a data set of 205 images of shoot apical meristems representing 91 species of bryophytes, lycophytes, and ferns. In parallel, we developed a mathematical and computational model to determine whether the meristem structural types observed empirically are predicted from Sachs's division rules; namely, cells divide symmetrically while positioning their new wall at a right angle to the parental walls.
According to our data set, only four meristem structural types are observed in nature, corresponding to apical cells dividing along one, two, three, or four faces. In addition, the prevalence of the structural types in diverse plant lineages correlates with the shape of the meristems on which they are found. Our model based on Sachs's division rules indicates that as much as six meristem structural types are geometrically possible, but only the four types observed empirically are dynamically stable for realistic meristem geometries.
Simple division rules, which we interpret as biophysical constraints on the assembly of the preprophase band, may therefore explain the cellular organization of the shoot apical meristem in three major groups of land plants.
陆地植物的顶端分生组织在复杂茎结构的进化中发挥了重要作用。苔藓植物、石松类植物和蕨类植物茎顶端分生组织最常见的结构特征是单个顶端细胞被一圈顶端衍生细胞围绕。尽管这种分生组织组织类型很重要，但目前尚不清楚它在顶端是如何维持的。
我们分析了一个包含205张茎顶端分生组织图像的数据集内不同分生组织组织类型的分布情况，这些图像代表了91种苔藓植物、石松类植物和蕨类植物。同时，我们开发了一个数学和计算模型，以确定根据经验观察到的分生组织结构类型是否可以从萨克斯的分裂规则中预测出来；也就是说，细胞对称分裂，同时将新壁定位成与亲代壁成直角。
根据我们的数据集，在自然界中仅观察到四种分生组织结构类型，分别对应顶端细胞沿一个、两个、三个或四个面分裂。此外，不同植物谱系中这些结构类型的普遍性与其所在分生组织的形状相关。我们基于萨克斯分裂规则的模型表明，在几何上最多可能有六种分生组织结构类型，但对于实际的分生组织几何形状而言，只有根据经验观察到的四种类型是动态稳定的。
因此，我们解释为对前期带组装的生物物理限制的简单分裂规则，可能解释了三大类陆地植物茎顶端分生组织的细胞组织。
