Comparative anatomy of embryogenesis in three species of Podostemaceae and evolution of the loss of embryonic shoot and root meristems
Comparative anatomy of embryogenesis in three species of Podostemaceae and evolution of the loss of embryonic shoot and root meristems
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DOI：
10.1111/j.1525-142x.2011.00488.x
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发表时间：
2011-07-01
影响因子：
2.9
通讯作者：
Yamada, Toshihiro
中科院分区：
文献类型：
--
作者：
Katayama, Natsu;Kato, Masahiro;Yamada, Toshihiro
在被子植物的胚胎发生过程中，胚的芽和根分生组织在胚的相对两极形成，形成垂直的体表。然而，水生菊科Podostemaceae表现出不寻常的水平形体计划，这归因于胚胎芽和根分生组织的丧失。为了推测这些分生组织丧失的胚胎发生变化，我们对具有不同分生组织特征的三种植物的胚胎发生进行了研究，即具有明显的茎和根分生组织的短绒芥、具有减少的茎和无根分生组织的泽兰和无茎和无根分生组织的日本水仙。与其他植物一样，短叶参的组织中心（OC）和L1层（表皮细胞层）产生了一个独特的茎分生组织，而下垂体形成了根分生组织的静止中心（QC）。地衣有一个形态上无法识别的茎分生组织，因为一个明显的L1层没有发育，而假定的OC前体正常产生。在日本辣椒中，八细胞胚顶端细胞的垂直分裂阻碍了假定的胚轴形成。在地衣和日本姜中，假设的QC未能启动，是因为胚轴在早期胚胎发生时重复纵向分裂。基于它们的系统发育关系，我们推断，在豆科植物中，常规胚茎分生组织的丢失经历了两个步骤，即L1层的丢失和OC的丢失，而胚根分生组织的丢失则发生在胚乳的错误描述中。
During embryogenesis in angiosperms, the embryonic shoot and root meristems are created at opposite poles of the embryo, establishing a vertical body plan. However, the aquatic eudicot family Podostemaceae exhibits an unusual horizontal body plan, which is attributed to the loss of embryonic shoot and root meristems. To infer the embryogenetic changes responsible for the loss of these meristems, we examined the embryogenesis of three podostemads with different meristem characters, that is, Terniopsis brevis with distinct shoot and root meristems, Zeylanidium lichenoides with reduced shoot and no root meristems, and Hydrobryum japonicum with no shoot and no root meristems. In T. brevis, as in other eudicots, the putative organizing center (OC) and L1 layer (=the epidermal cell layer) arose to generate a distinct shoot meristem initial, and the hypophysis formed the putative quiescent center (QC) of a root meristem. Z. lichenoides had a morphologically unrecognizable shoot meristem, because a distinct L1 layer did not develop, whereas the putative OC precursor arose normally. In H. japonicum, the vertical divisions of the apical cells of eight-cell embryo prevented putative OC initiation. In Z. lichenoides and H. japonicum, the putative QC failed to initiate because the hypophysis repeated longitudinal divisions during early embryogenesis. Based on their phylogenetic relationships, we infer that the conventional embryonic shoot meristem was lost in Podostemaceae via two steps, that is, the loss of a distinct L1 layer and the loss of the OC, whereas the loss of the embryonic root meristem occurred once by misspecification of the hypophysis.