Abstract
Silicon (Si) accumulation protects plants from biotic and abiotic stresses. It is transported and distributed within the plant body through a cooperative system of channel type (e.g., OsLsi1) and efflux (Lsi2s e.g., OsLsi2) Si transporters (SITs) that belong to Noduline-26 like intrinsic protein family of aquaporins and an uncharacterized anion transporter family, respectively. Si is deposited in plant tissues as phytoliths and the process is known as biosilicification but the knowledge about the proteins involved in this process is limited. In the present study, we explored channel type SITs and Lsi2s, and siliplant1 protein (Slp1) in 80 green plant species. We found 80 channel type SITs and 133 Lsi2s. The channel type SITs characterized by the presence of two NPA motifs, GSGR or STAR selectivity filter, and 108 amino acids between two NPA motifs were absent from Chlorophytes, while Streptophytes evolved two different types of channel type SITs with different selectivity filters. Both channel type SITs and Lsi2s evolved two types of gene structures each, however, Lsi2s are ancient and were also found in Chlorophyta. Homologs of Slp1 (225) were present in almost all Streptophytes regardless of their Si accumulation capacity. In Si accumulator plant species, the Slp1s were characterized by the presence of H, D-rich domain, P, K, E-rich domain, and P, T, Y-rich domain, while moderate Si accumulators lacked H, D-rich domain and P, T, Y-rich domains. The digital expression analysis and coexpression networks highlighted the role of channel type and Lsi2s, and how Slp1 homologs were ameliorating plants’ ability to withstand different stresses by co-expressing with genes related to structural integrity and signaling. Together, the in-silico exploration made in this study increases our knowledge of the process of biosilicification in plants.
Highlights
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]
The screening for STAR or GSGR SF and two NPA motifs resulted in 80 genes [10]
Current results are clearly in agreement with earlier reports that channel type Si transporters (SITs) are widespread in monocots, since we found a higher number of channel type SITs in all studied members of Poaceae (Table 2)
Summary
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. In soil, Si is present as monosilicic acid [Si(OH)4 ] at pH 9 with variable concentrations based on soil type [3]. Silicic acid is taken up through a cooperative system of channel type Si transporters (SITs) and efflux silicon transporters (homologs of OsLsi, on Lsi2s) [4].
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