Koi Satoshi, Katayama Natsu
Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan.
Methods Mol Biol. 2013;959:83-95. doi: 10.1007/978-1-62703-221-6_5.
Podostemaceae is a family of aquatic angiosperms growing submerged on rocks in fast-flowing water and called moss-like or alga-like riverweeds. It evolved remarkable innovations to adapt to such an extreme environment, one of which is reduced shoots borne on roots adhering to rock surface. Recent observations revealed that the basal subfamily Tristichoideae, like most other angiosperms, has typical shoot apical meristems (SAMs). In species of the subfamily Podostemoideae, however, shoot apical meristems (SAMs) are not formed during development and new leaves arise from the meristematic basal region of preexisting leaves. The genetic basis of this shoot organogenesis process, e.g., the expression patterns of genes homologous to transcription factors regulating shoot development, is essential to better understand the evolution of Podostemaceae. A gene expression analysis found that the SAM-less Podostemoideae leaf has mixed identity of SAM and leaf, and provided insight into the evolution of the shoot in Podostemaceae.
川苔草科是一类水生被子植物，生长在水流湍急的岩石上，呈淹没状态，被称为苔藓状或藻类状水草。为适应这种极端环境，该科植物进化出了显著的适应性特征，其中之一是根上着生的缩短茎附着在岩石表面。最近的观察表明，基部亚科三肋苔亚科与大多数其他被子植物一样，具有典型的茎尖分生组织（SAMs）。然而，在川苔草亚科的物种中，发育过程中不会形成茎尖分生组织（SAMs），新叶从已存在叶片的分生基部区域产生。这种茎器官发生过程的遗传基础，例如与调控茎发育的转录因子同源的基因的表达模式，对于更好地理解川苔草科的进化至关重要。一项基因表达分析发现，无茎尖分生组织的川苔草亚科叶片具有茎尖分生组织和叶片的混合特征，并为川苔草科茎的进化提供了见解。
