Caractérisation du mécanisme d'absorption du silicium par Equisetum arvense

Authors: Grégoire, Caroline
Advisor: Bélanger, Richard R.Belzile, François
Abstract: Silicon (Si) is an abundant element in the environment. Plants benefit greatly from Si absorption, which results in increased resistance to stresses. There appears to be a link between high Si absorption via specific transporters, and the beneficial effects linked to this element. Recently, two groups of Si influx and efflux transporter were identified in the roots of Si-accumulating higher plants. Horsetail (Equisetum arvense) is a primitive plant and one of the strongest Si accumulators in the plant kingdom. The main objective of this thesis was to identify and characterize horsetail Si transporters. By sequencing the horsetail root transcriptome, we identified a multigene family of aquaporin Si influx transporters: aquaporins of the subgroup NIP. Comparison of known functional domains and phylogenetic analysis of sequences revealed that the horsetail proteins belong to a different group than higher-plant Si transporters. The horsetail proteins contain a STAR pore as opposed to the GSGR pore common to all previously identified Si influx transporters. In order to determine its functionality, the proteins were heterologously expressed in both Xenopus oocytes and Arabidopsis, and the results showed high Si influx activity. We also identified in horsetail two homologues of Lsi2 Si efflux transporters that share low sequence identity with their higher plant homologues. In order to determine its functionality, one of the horsetail Lsi2 was heterologously expressed in Xenopus oocytes, confirming its Si efflux activity. Overall, high Si accumulation by horsetail may be linked to the number of Si influx and efflux transporter, but also to their high transport activity. These findings on horsetail Si transporters allow a comparison between primitive plants and agronomic species, to optimize the use of Si against stresses.
Document Type: Thèse de doctorat
Issue Date: 2013
Open Access Date: 19 April 2018
Grantor: Université Laval
Collection:Thèses et mémoires

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