The Evolutionary Gap of Silicon Accumulation in Plants: Identifying Mechanisms of Silicon Transport in the Horsetail Fern Equisetum

Abstract

The global cycling of silicon, the second most abundant element in the Earth's crust, is a process driven almost entirely by biological organisms. Silicon accumulation and cycling plays a major role in controlling the global carbon cycle by fertilizing terrestrial and aquatic photosynthetic organisms, which, in turn, influences global climate. Today, grasses are the dominant organisms in the terrestrial cycle, but there are many other plants that also accumulate weight-percent silicon in their leaves. The relatively young age of grasses suggests that, in the past, there were most likely other species of plants which controlled the global terrestrial silicon cycle. We aim to reconstruct the evolution of silicon uptake by examining the mechanisms of accumulation in early-diverging plant lineages, specifically the fern Equisetum, commonly known as the horsetail. After extracting and reverse transcribing RNA from different species of Equisetum, we attempted to amplify silicon transporter sequences using primers previously developed for Equisetum arvense. After amplification, we observed a band in our gel analysis, indicating that a gene was successfully cloned. By analyzing these sequences and comparing them to existing sequences in more recent plant lineages, we will be able to determine if methods of silicon accumulation are conserved across species. This information will allow us to reconstruct the history of the terrestrial silicon cycle, putting us in a better position to understand how plants have shaped, and will continue to shape, terrestrial ecosystems and global climate