Abstract：
The conquest of land by plants was concomitant with, and possibly enabled by, the evolution of three-dimensional (3D) growth. The moss Physcomitrium patens provides a model system for elucidating molecular mechanisms in the initiation of 3D growth. Here, we investigate whether the phytohormone ethylene, which is believed to have been a signal before land plant emergence, plays a role in 3D growth regulation in P. patens. We report ethylene controls 3D gametophore formation, based on results from exogenously applied ethylene and genetic manipulation of PpEIN2, which is a central component in the ethylene signaling pathway. Overexpression (OE) of PpEIN2 activates ethylene responses and leads to earlier formation of gametophores with fewer gametophores produced thereafter, phenocopying ethylene-treated wild-type. Conversely, Ppein2 knockout mutants, which are ethylene insensitive, show initially delayed gametophore formation with more gametophores produced later. Furthermore, pharmacological and biochemical analyses reveal auxin levels are decreased in the OE lines but increased in the knockout mutants. Our results suggest that evolutionarily, ethylene and auxin molecular networks were recruited to build the plant body plan in ancestral land plants. This might have played a role in enabling ancient plants to acclimate to the continental surfaces of the planet.
摘要：
植物对土地的征服伴随着，可能由，三维(3D)生长的演变。苔藓Physcomitriumpatens提供了一个模型系统，用于阐明3D生长开始的分子机制。这里,我们研究植物激素乙烯，这被认为是陆地植物出现之前的信号，在P.patens的3D生长调节中起作用。我们报告乙烯控制3D配子体的形成，基于外源应用乙烯和PpEIN2基因操作的结果，PpEIN2是乙烯信号通路中的核心成分。PpEIN2的过表达（OE）激活乙烯反应，并导致配子体的早期形成，此后产生的配子体较少。表型复制乙烯处理的野生型。相反，Ppein2基因敲除突变体,对乙烯不敏感，显示最初延迟的配子体形成，后来产生更多的配子体。此外，药理和生化分析表明，OE系的生长素水平降低，但敲除突变体的生长素水平升高。我们的结果表明，在进化上，招募乙烯和生长素分子网络来构建祖先陆地植物的植物体计划。这可能在使古代植物适应地球大陆表面方面发挥了作用。
