New evidence defining the evolutionary path of aquaporins regulating silicon uptake in land plants

Understanding the evolution events defining silicon (Si) uptake in plant species is important for the efficient exploration of Si-derived benefits. In the present study, Si accumulation was studied in 456 diverse plant species grown in uniform field conditions, and in a subset of 151 species grown under greenhouse conditions allowing efficient comparison among the species. In addition, a systematic analysis of nodulin 26-like intrinsic proteins III (NIPIII), which form Si channels, was performed in over 1000 species to trace their evolutionary path and link with Si accumulation. Significant variations in Si accumulation were observed among the plant species studied. For their part, species lacking NIP-IIIs systematically showed low Si accumulation. Interestingly, seven NIP-IIIs were identified in three moss species, namely Physcomitrella patens, Andreaea rupestris, and Scouleria aquatic, indicating that the evolution of NIP-IIIs dates back as early as 515 Ma. These results were further supported from previous reports of Si deposition in moss fossils estimated to be from around the Ordovician era. The taxonomical distribution provided in the present study will be helpful for several other disciplines, like palaeoecology and geology, that define the biogeochemical cycling of Si. In addition to the prediction of Si uptake potential of plant species based on sequence information and taxonomical positioning, the evolutionary path of Si uptake mechanism described here will be helpful to understand the Si environment over the different eras of land plant evolution.

Keywords: aquaporins; genomics; mosses; nodulin 26-like intrinsic proteins; plant evolution; silicon.