期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：17
页码：5449-5454
DOI：10.1073/pnas.1500289112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceAmorphous silica (SiO2) phases produced by plants are principal mass fluxes in the global silica cycle. The study of silica biomineralization in plants has largely focused on angiosperms, leaving open questions about its early evolution. To address the effect of early plants on the silica cycle, we measured the silica contents of extant members of plant groups known from fossils to have been major components of the terrestrial landscape in the past, as grasses are today. Most of these early-diverging plant lineages accumulate substantial amounts of silica. We compared these observations with the distribution and evolution of plant silica transport proteins, suggesting convergent evolution of silica use. Results presented here outline an extensive evolutionary history of silica biomineralization in plants. Biomineralization plays a fundamental role in the global silicon cycle. Grasses are known to mobilize significant quantities of Si in the form of silica biominerals and dominate the terrestrial realm today, but they have relatively recent origins and only rose to taxonomic and ecological prominence within the Cenozoic Era. This raises questions regarding when and how the biological silica cycle evolved. To address these questions, we examined silica abundances of extant members of early-diverging land plant clades, which show that silica biomineralization is widespread across terrestrial plant linages. Particularly high silica abundances are observed in lycophytes and early-diverging ferns. However, silica biomineralization is rare within later-evolving gymnosperms, implying a complex evolutionary history within the seed plants. Electron microscopy and X-ray spectroscopy show that the most common silica-mineralized tissues include the vascular system, epidermal cells, and stomata, which is consistent with the hypothesis that biomineralization in plants is frequently coupled to transpiration. Furthermore, sequence, phylogenetic, and structural analysis of nodulin 26-like intrinsic proteins from diverse plant genomes points to a plastic and ancient capacity for silica accumulation within terrestrial plants. The integration of these two comparative biology approaches demonstrates that silica biomineralization has been an important process for land plants over the course of their >400 My evolutionary history.
