Molecular mechanisms of phosphate and sulphate transport in plants

Abstract

The application of molecular techniques in recent years has advanced our understanding of phosphate and sulphate transport processes in plants. Genes encoding phosphate and sulphate transporters have been isolated from a number of plant species. The transporters encoded by these genes are related to the major facilitator superfamily of proteins. They are predicted to contain 12 membrane-spanning domains and function as H(+)/H(2)PO(-4) or H(+)/SO(2/-4) cotransporters. Both high-affinity and low-affinity types have been identified. Most research has concentrated on genes that encode transporters expressed in roots. The expression of many of these genes is transcriptionally regulated by signals that respond to the nutrient status of the plant. Nutrient demand and the availability of precursors needed in the assimilatory pathways also regulate transcription of some of these genes. Information on the cell types in which phosphate and sulphate transporters are expressed is becoming available. These data, together with functional characterisation of the transporters, are enabling the roles of various transporters in the overall phosphate and sulphate nutrition of plants to be defined.

Cadmium-Induced Sulfate Uptake in Maize Roots

“…Molecular (Smith et al, 1995(Smith et al, , 2000 and kinetic (Hawkesford et al, 1993;Smith et al, 1995Smith et al, , 1997 studies indicate that sulfate uptake is energetically coupled to the H ϩ -electrochemical gradient (⌬ H ϩ ) across the plasma membrane, through H ϩ -SO 4 2Ϫ symport mechanisms. Changes in ⌬ H ϩ may influence the activity of H ϩ -symporters (Hawkesford et al, 1993;Chrispeels et al, 1999).…”

“…Several high-affinity sulfate transporters and lowaffinity sulfate transporters have been cloned and characterized with respect to their kinetic profiles and regulation, enlarging our knowledge on the con-trol of the sulfur fluxes in higher plants (Leustek and Saito, 1999;Saito, 2000;Smith et al, 2000). These transporters may have specialized functions, because they differ in affinity for sulfate and in spatial expression.…”

Diversity in phosphorus mobilisation and uptake in ectomycorrhizal fungi

“…However, in natural conditions, approximately 80% of land plants live in association with specialised soil fungi to form mycorrhizal roots. The most widespread mycorrhizal association exists between herbaceous plants and arbuscular mycorrhizal (AM) fungi forming AM symbiosis (Parniske 2008;Smith and Read 2008). Woody plants from the gymnosperms and several angiosperms growing in boreal and temperate regions also live in symbiotic association with mycorrhizal fungi that form ectomycorrhizal (ECM) roots (Marmeisse et al 2004).…”

“…The formation of mycorrhizal roots is considered as the most widespread response to increase phosphate acquisition by plants (Burleigh et al 2002;Smith et al 2000;Tibbett and Sanders 2002). This is mainly due to the repeated observation that mycorrhizal plants show growth improvement and increased plant P content than non-mycorrhizal plants (Chalot et al 2002;Smith and Read 2008).…”

“…This is mainly due to the repeated observation that mycorrhizal plants show growth improvement and increased plant P content than non-mycorrhizal plants (Chalot et al 2002;Smith and Read 2008). Three main hypotheses have been proposed to explain this improved P nutrition of mycorrhizal plants: an increase of (1) P mobilisation from mineral P, (2) P mobilisation from organic P and (3) soil exploration and P uptake.…”