title: Identification and characterization of silicon efflux transporters in horsetail (Equisetum arvense).
abstract: Silicon (Si) is a beneficial element to plants, and its absorption via transporters leads to protective effects against biotic and abiotic stresses. In higher plants, two groups of root transporters for Si have been identified: influx transporters (Lsi1) and efflux transporters (Lsi2). Lsi1 transporters belong to the NIPIII aquaporins, and functional Lsi1s have been found in many plants species. Much less is known about Lsi2s that have been characterized in only a few species. Horsetail (Equisetum arvense), known among the highest Si accumulators in the plant kingdom, is a valuable model to study Si absorption and deposition. In this study, we first analyzed discrete Si deposition patterns in horsetail shoots, where ubiquitous silicification differs markedly from that of higher plants. Then, using the sequenced horsetail root transcriptome, two putative Si efflux transporter genes, EaLsi2-1 and EaLsi2-2, were identified. These genes share low sequence similarity with their homologues in higher plants. Further characterisation of EaLsi2-1 in transient expression assay using Nicotiana benthamiana epidermal cells confirmed transmembrane localization. In order to determine their functionality, the EaLsi2-1 was expressed in Xenopus oocytes, confirming that the translated protein was efficient for Si efflux. Both genes were equally expressed in roots and shoots, but interestingly, showed a much higher expression in the shoots than in the roots in contrast to Lsi2s found in other plants, a result consistent with the specific anatomy of horsetail and its rank as one of the highest Si accumulators among plant species.
authors.affiliation: Département de Phytologie-Faculté des Sciences de l'agriculture et de l'alimentation, Centre de recherche en horticulture, Université Laval, Pavillon Paul-Comtois, Québec, G1V 0A6 QC, Canada.
authors.forename: Julien
authors.initials: J
authors.lastname: Vivancos
authors.affiliation: Département de Phytologie-Faculté des Sciences de l'agriculture et de l'alimentation, Centre de recherche en horticulture, Université Laval, Pavillon Paul-Comtois, Québec, G1V 0A6 QC, Canada.
authors.forename: Rupesh
authors.initials: R
authors.lastname: Deshmukh
authors.affiliation: Département de Phytologie-Faculté des Sciences de l'agriculture et de l'alimentation, Centre de recherche en horticulture, Université Laval, Pavillon Paul-Comtois, Québec, G1V 0A6 QC, Canada.
authors.forename: Caroline
authors.initials: C
authors.lastname: Grégoire
authors.affiliation: Département de Phytologie-Faculté des Sciences de l'agriculture et de l'alimentation, Centre de recherche en horticulture, Université Laval, Pavillon Paul-Comtois, Québec, G1V 0A6 QC, Canada.
authors.forename: Wilfried
authors.initials: W
authors.lastname: Rémus-Borel
authors.affiliation: Département de Phytologie-Faculté des Sciences de l'agriculture et de l'alimentation, Université Laval, Pavillon Charles-Eugène-Marchand, Québec, G1V 0A6 QC, Canada.
authors.forename: François
authors.initials: F
authors.lastname: Belzile
authors.affiliation: Département de Phytologie-Faculté des Sciences de l'agriculture et de l'alimentation, Centre de recherche en horticulture, Université Laval, Pavillon Paul-Comtois, Québec, G1V 0A6 QC, Canada. Electronic address: richard.belanger@fsaa.ulaval.ca.
authors.forename: Richard R
authors.initials: RR
authors.lastname: Bélanger
mesh_terms: D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D020829:Equisetum / Q000235:genetics / Q000378:metabolism*; D017343:Genes, Plant; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018520:Plant Shoots / Q000378:metabolism; D016415:Sequence Alignment; D012825:Silicon / Q000378:metabolism*; D014981:Xenopus
chemical_list: D018076:DNA, Complementary; D026901:Membrane Transport Proteins; D010940:Plant Proteins; D012825:Silicon
keywords: Efflux transporter; Equisetum arvense; Lsi2 genes; Silicon transport; Triticum aestivum; Xenopus oocytes