PNAS:古代地球的植物定植

法国图卢兹大学植物科学研究所一项研究发现，所有现存陆地植物的最晚近共同祖先拥有一种预先存在的适应性，这很可能让它能够与有益的真菌相互作用，最终在地球贫瘠的表面扎下根。植物在大约4.5亿年前在陆地定植，这是一个在根本上重新配置了气候、建立了陆地生态系统并且刺激了动物进化的分水岭时刻。然而，最早的陆地植物如何在一个似乎贫瘠的环境中生存足够长的时间从而成功地确立自身的存在，这仍然不清楚。Pierre-Marc Delaux及其同事分析了某些已知最早的陆地植物和绿藻的DNA和RNA，发现了证据表明现代植物中的一种关键的共生信号传导路径在植物在陆地上扎下根来之前就部分存在了。这个路径使用钙和钙调节蛋白依赖性蛋白激酶调控一种与丛枝菌根的共生，这是以碳作为交换而帮助植物根从土壤中获得营养和水的真菌。这组作者说，此外，这种关系所需的基因在植物做出这种转变之后持续发展，这提示这种共生在这种起源祖先的后继世代中持续进化。

原文链接：

Algal ancestor of land plants was preadapted for symbiosis

原文摘要：

Colonization of land by plants was a major transition on Earth, but the developmental and genetic innovations required for this transition remain unknown. Physiological studies and the fossil record strongly suggest that the ability of the first land plants to form symbiotic associations with beneficial fungi was one of these critical innovations. In angiosperms, genes required for the perception and transduction of diffusible fungal signals for root colonization and for nutrient exchange have been characterized. However, the origin of these genes and their potential correlation with land colonization remain elusive. A comprehensive phylogenetic analysis of 259 transcriptomes and 10 green algal and basal land plant genomes, coupled with the characterization of the evolutionary path leading to the appearance of a key regulator, a calcium- and calmodulin-dependent protein kinase, showed that the symbiotic signaling pathway predated the first land plants. In contrast, downstream genes required for root colonization and their specific expression pattern probably appeared subsequent to the colonization of land. We conclude that the most recent common ancestor of extant land plants and green algae was preadapted for symbiotic associations. Subsequent improvement of this precursor stage in early land plants through rounds of gene duplication led to the acquisition of additional pathways and the ability to form a fully functional arbuscular mycorrhizal symbiosis.

doi: 10.1073/PNAS.1515426112

作者：Pierre-Marc Delaux