Jaeger Richard, Moody Laura A
Department of Plant Sciences, University of Oxford, Oxford, UK.
Evol Dev. 2021 May;23(3):123-136. doi: 10.1111/ede.12376. Epub 2021 Apr 6.
One of the most defining moments in history was the colonization of land by plants approximately 470 million years ago. The transition from water to land was accompanied by significant changes in the plant body plan, from those than resembled filamentous representatives of the charophytes, the sister group to land plants, to those that were morphologically complex and capable of colonizing harsher habitats. The moss Physcomitrium patens (also known as Physcomitrella patens) is an extant representative of the bryophytes, the earliest land plant lineage. The protonema of P. patens emerges from spores from a chloronemal initial cell, which can divide to self-renew to produce filaments of chloronemal cells. A chloronemal initial cell can differentiate into a caulonemal initial cell, which can divide and self-renew to produce filaments of caulonemal cells, which branch extensively and give rise to three-dimensional shoots. The process by which a chloronemal initial cell differentiates into a caulonemal initial cell is tightly regulated by auxin-induced remodeling of the actin cytoskeleton. Studies have revealed that the genetic mechanisms underpinning this transition also regulate tip growth and differentiation in diverse plant taxa. This review summarizes the known cellular and molecular mechanisms underpinning the chloronema to caulonema transition in P. patens.
历史上最具决定性的时刻之一是大约4.7亿年前植物对陆地的殖民。从水到陆地的转变伴随着植物身体结构的显著变化，从那些类似于轮藻（陆地植物的姐妹类群）的丝状代表，到那些形态复杂且能够在更恶劣栖息地殖民的植物。小立碗藓（也称为小立碗藓）是苔藓植物的现存代表，苔藓植物是最早的陆地植物谱系。小立碗藓的原丝体从孢子中的一个绿丝体初始细胞产生，该细胞可以分裂自我更新以产生绿丝体细胞丝。一个绿丝体初始细胞可以分化为轴丝体初始细胞，轴丝体初始细胞可以分裂并自我更新以产生轴丝体细胞丝，轴丝体细胞丝广泛分支并形成三维枝条。绿丝体初始细胞分化为轴丝体初始细胞的过程受到生长素诱导的肌动蛋白细胞骨架重塑的严格调控。研究表明，支撑这种转变的遗传机制也调节不同植物类群中的顶端生长和分化。本综述总结了已知的支撑小立碗藓绿丝体到轴丝体转变的细胞和分子机制。
