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Kumar S, Adiram-Filiba N, Blum S, Sanchez-Lopez JA, Tzfadia O, Omid A, Volpin H, Heifetz Y, Goobes G, Elbaum R. Siliplant1 protein precipitates silica in sorghum silica cells. J Exp Bot 2020; 71:6830-6843. [PMID: 32485738 DOI: 10.1093/jxb/eraa258] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 05/26/2020] [Indexed: 05/26/2023]
Abstract
Silicon is absorbed by plant roots as silicic acid. The acid moves with the transpiration stream to the shoot, and mineralizes as silica. In grasses, leaf epidermal cells called silica cells deposit silica in most of their volume using an unknown biological factor. Using bioinformatics tools, we identified a previously uncharacterized protein in Sorghum bicolor, which we named Siliplant1 (Slp1). Slp1 is a basic protein with seven repeat units rich in proline, lysine, and glutamic acid. We found Slp1 RNA in sorghum immature leaf and immature inflorescence. In leaves, transcription was highest just before the active silicification zone (ASZ). There, Slp1 was localized specifically to developing silica cells, packed inside vesicles and scattered throughout the cytoplasm or near the cell boundary. These vesicles fused with the membrane, releasing their content in the apoplastic space. A short peptide that is repeated five times in Slp1 precipitated silica in vitro at a biologically relevant silicic acid concentration. Transient overexpression of Slp1 in sorghum resulted in ectopic silica deposition in all leaf epidermal cell types. Our results show that Slp1 precipitates silica in sorghum silica cells.
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Affiliation(s)
- Santosh Kumar
- Robert H Smith Institute of Plant Sciences and Genetics in Agriculture, Robert H Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel
| | | | - Shula Blum
- Robert H Smith Institute of Plant Sciences and Genetics in Agriculture, Robert H Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel
| | - Javier Arturo Sanchez-Lopez
- Department of Entomology, Robert H Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel
| | - Oren Tzfadia
- Bioinformatics and Systems Biology, VIB/Ghent University, Gent, Belgium
| | - Ayelet Omid
- Danziger Innovations Limited, Mishmar Hashiva, Israel
| | - Hanne Volpin
- Danziger Innovations Limited, Mishmar Hashiva, Israel
| | - Yael Heifetz
- Department of Entomology, Robert H Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel
| | - Gil Goobes
- Department of Chemistry, Bar-Ilan University, Ramat Gan, Israel
| | - Rivka Elbaum
- Robert H Smith Institute of Plant Sciences and Genetics in Agriculture, Robert H Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel
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