Phytolith Formation in Plants: From Soil to Cell

Abstract

Silica is deposited extra- and intracellularly in plants in solid form, as phytoliths. Phytoliths have emerged as accepted taxonomic tools and proxies for reconstructing ancient flora, agricultural economies, environment, and climate. The discovery of silicon transporter genes has aided in the understanding of the mechanism of silicon transport and deposition within the plant body and reconstructing plant phylogeny that is based on the ability of plants to accumulate silica. However, a precise understanding of the process of silica deposition and the formation of phytoliths is still an enigma and the information regarding the proteins that are involved in plant biosilicification is still scarce. With the observation of various shapes and morphologies of phytoliths, it is essential to understand which factors control this mechanism. During the last two decades, significant research has been done in this regard and silicon research has expanded as an Earth-life science superdiscipline. We review and integrate the recent knowledge and concepts on the uptake and transport of silica and its deposition as phytoliths in plants. We also discuss how different factors define the shape, size, and chemistry of the phytoliths and how biosilicification evolved in plants. The role of channel-type and efflux silicon transporters, proline-rich proteins, and siliplant1 protein in transport and deposition of silica is presented. The role of phytoliths against biotic and abiotic stress, as mechanical barriers, and their use as taxonomic tools and proxies, is highlighted.

Molecular and Functional Characterization of Grapevine NIPs through Heterologous Expression in aqy-Null Saccharomyces cerevisiae

“…Expression of the mutated protein with longer C-terminal appeared to have higher permeability not only for glycerol but also for water ( Figures 3 and 4). Studies suggest that besides ar/R composition, precise amino acid stretch (108 amino acids) between the NPA motifs is also crucial for substrate selectivity and permeability [30,31]. To observe this requirement in grapevine NIPs for water and glycerol transport, obtained sequences were aligned with the representative NIPs sequences of their group.…”

“…Thereafter, the phosphate-starved cells were subjected to grow in the presence of As (V), under phosphate-replete condition, showing abolished arsenate toxicity in these strains. Obtained data points of the curve were fitted to the ComBase tool DMFit (online) [30] and growth parameters like specific growth rate (h −1 ) and final biomass of the fits were estimated (Table S2). Data is represented in the mean ± SD of at least two independent experiments with three replicates.…”

“…Yeast cells expressing empty plasmid pUG35 or grapevine NIPs were washed and inoculated (A 260 = 0.1) in the minimal media containing test substrates. Obtained data points of the curve were fitted to the ComBase tool DMFit (online) [30] and growth parameters like lag phase (h), specific growth rate (h −1 ), and final biomass of the fits were estimated (Table S2). Data is represented in the mean ± SD of at least two independent experiments with three replicates.…”

In-silico Exploration of Channel Type and Efflux Silicon Transporters and Silicification Proteins in 80 Sequenced Viridiplantae Genomes

“…Silicon (Si) exerts beneficial effects on the growth and productivity of plants and has been recognized as a beneficial element by the International Plant Nutrition Institute [ 1 ]. Decades of research on Si have authenticated its importance towards plant’s ability to withstand biotic and abiotic stresses [ 2 ]. Si accumulation in plants is regarded as beneficial regardless of their Si accumulation capacity; when deprived of Si, plants are susceptible to stresses as compared to the ones grown in Si.…”

“…The rice Lsi2 ( OsLsi2 ) has 11 predicted transmembrane domains (TMDs) and it belongs to an uncharacterized anion transporter family. It lacks homology with channel type SIT and limited studies have described any conserved characteristics within the characterized as well as predicted Lsi2s [ 2 , 11 ]. The cooperative system of both channel type SITs and Lsi2s enable plants to translocate Si to the aerial parts of the plants where it is deposited as amorphous Si(SiO 2 ) [ 12 ].…”