Delaux Pierre-Marc, Radhakrishnan Guru V, Jayaraman Dhileepkumar, Cheema Jitender, Malbreil Mathilde, Volkening Jeremy D, Sekimoto Hiroyuki, Nishiyama Tomoaki, Melkonian Michael, Pokorny Lisa, Rothfels Carl J, Sederoff Heike Winter, Stevenson Dennis W, Surek Barbara, Zhang Yong, Sussman Michael R, Dunand Christophe, Morris Richard J, Roux Christophe, Wong Gane Ka-Shu, Oldroyd Giles E D, Ané Jean-Michel
Department of Agronomy, University of Wisconsin, Madison, WI 53706; John Innes Centre, Norwich NR4 7UH, United Kingdom;
John Innes Centre, Norwich NR4 7UH, United Kingdom;
Proc Natl Acad Sci U S A. 2015 Oct 27;112(43):13390-5. doi: 10.1073/pnas.1515426112. Epub 2015 Oct 5.
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.
植物在陆地上的定殖是地球生命史上的一次重大转变，但实现这一转变所需的发育和遗传创新仍不为人知。生理学研究和化石记录有力地表明，最早的陆地植物与有益真菌形成共生关系的能力是这些关键创新之一。在被子植物中，参与感知和转导可扩散真菌信号以实现根部定殖和营养交换的基因已得到鉴定。然而，这些基因的起源以及它们与陆地定殖的潜在关联仍然不明。对259个转录组以及10个绿藻和基部陆地植物基因组进行的全面系统发育分析，再加上对导致关键调节因子（一种钙和钙调蛋白依赖性蛋白激酶）出现的进化路径的表征，结果表明共生信号通路早于最早的陆地植物出现。相比之下，根部定殖所需的下游基因及其特定表达模式可能在陆地定殖之后才出现。我们得出结论，现存陆地植物和绿藻的最近共同祖先已预先适应了共生关系。早期陆地植物通过一轮又一轮的基因复制对这一初始阶段进行了后续改进，从而获得了更多途径以及形成功能完备的丛枝菌根共生的能力。
