Howard Hughes Medical Institute, Jack H. Skirball Center for Chemical Biology and Proteomics, The Salk Institute for Biological Studies La Jolla, CA, USA.
Front Plant Sci. 2013 May 10;4:119. doi: 10.3389/fpls.2013.00119. eCollection 2013.
Early plants began colonizing the terrestrial earth approximately 450 million years ago. Their success on land has been partially attributed to the evolution of specialized metabolic systems from core metabolic pathways, the former yielding structurally and functionally diverse chemicals to cope with a myriad of biotic and abiotic ecological pressures. Over the past two decades, functional genomics, primarily focused on flowering plants, has begun cataloging the biosynthetic players underpinning assorted classes of plant specialized metabolites. However, the molecular mechanisms enriching specialized metabolic pathways during land plant evolution remain largely unexplored. Selaginella is an extant lycopodiophyte genus representative of an ancient lineage of tracheophytes. Notably, the lycopodiophytes diverged from euphyllophytes over 400 million years ago. The recent completion of the whole-genome sequence of an extant lycopodiophyte, S. moellendorffii, provides new genomic and biochemical resources for studying metabolic evolution in vascular plants. 400 million years of independent evolution of lycopodiophytes and euphyllophytes resulted in numerous metabolic traits confined to each lineage. Surprisingly, a cadre of specialized metabolites, generally accepted to be restricted to seed plants, have been identified in Selaginella. Initial work suggested that Selaginella lacks obvious catalytic homologs known to be involved in the biosynthesis of well-studied specialized metabolites in seed plants. Therefore, these initial functional analyses suggest that the same chemical phenotypes arose independently more commonly than anticipated from our conventional understanding of the evolution of metabolism. Notably, the emergence of analogous and homologous catalytic machineries through convergent and parallel evolution, respectively, seems to have occurred repeatedly in different plant lineages.
早期植物大约在 4.5 亿年前开始在陆地殖民。它们在陆地上的成功部分归因于核心代谢途径中专门代谢系统的进化，前者产生结构和功能多样的化学物质，以应对无数的生物和非生物生态压力。在过去的二十年中，功能基因组学主要集中在开花植物上，已经开始对各种植物特化代谢物的生物合成参与者进行编目。然而，在陆地植物进化过程中丰富特化代谢途径的分子机制在很大程度上仍未得到探索。卷柏是现存石松植物属的代表，是维管植物的一个古老谱系。值得注意的是，石松植物与真叶植物在 4 亿多年前就已经分化。现存石松植物 S. moellendorffii 的全基因组序列的最近完成，为研究维管植物代谢进化提供了新的基因组和生化资源。4 亿年的石松植物和真叶植物的独立进化导致了许多代谢特征局限于每个谱系。令人惊讶的是，在卷柏中发现了一组特化代谢物，这些代谢物通常被认为局限于种子植物。最初的研究表明，卷柏缺乏明显的催化同源物，这些同源物已知参与种子植物中研究充分的特化代谢物的生物合成。因此，这些最初的功能分析表明，相同的化学表型比我们对代谢进化的传统理解所预期的更为常见地独立出现。值得注意的是，通过趋同和并行进化分别出现类似和同源的催化机制，似乎在不同的植物谱系中反复发生。
