Bryophytes are nonvascular spore-forming plants. Unlike in flowering plants, the gametophyte (haploid) generation of bryophytes dominates the sporophyte (diploid) generation. A comparison of bryophytes with flowering plants allows us to answer some fundamental questions raised in evolutionary cell and developmental biology. The moss Physcomitrium patens was the first bryophyte with a sequenced genome. Many cell and developmental studies have been conducted in this species using gene targeting by homologous recombination. The liverwort Marchantia polymorpha has recently emerged as an excellent model system with low genomic redundancy in most of its regulatory pathways. With the development of molecular genetic tools such as efficient genome editing, both P. patens and M. polymorpha have provided many valuable insights. Here, we review these advances with a special focus on polarity formation at the cell and tissue levels. We examine current knowledge regarding the cellular mechanisms of polarized cell elongation and cell division, including symmetric and asymmetric cell division. We also examine the role of polar auxin transport in mosses and liverworts. Finally, we discuss the future of evolutionary cell and developmental biological studies in plants.

中文翻译：

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苔藓植物 Physcommitrium patens 和 Marchantia polymorpha 作为研究植物进化细胞和发育生物学的模型系统

苔藓植物是非维管孢子形成植物。与开花植物不同，苔藓植物的配子体（单倍体）代主导着孢子体（二倍体）的产生。苔藓植物与开花植物的比较使我们能够回答进化细胞和发育生物学中提出的一些基本问题。苔藓 Physcommitrium patens 是第一个具有测序基因组的苔藓植物。许多细胞和发育研究已经在该物种中使用同源重组的基因靶向进行。地钱最近已成为一种优秀的模型系统，在其大多数调节途径中具有低基因组冗余。随着高效基因组编辑等分子遗传工具的发展，P. patens 和 M. polymorpha 都提供了许多有价值的见解。这里，我们回顾了这些进展，特别关注细胞和组织水平的极性形成。我们研究了有关极化细胞伸长和细胞分裂的细胞机制的当前知识，包括对称和不对称细胞分裂。我们还研究了极性生长素转运在苔藓和地钱中的作用。最后，我们讨论了植物进化细胞和发育生物学研究的未来。