Molecular mechanisms of phosphate and sulphate transport in plants

The application of molecular techniques in recent years has advanced our un derstanding of phosphate and sulphate transport processes in plants. Genes encoding phosphate and sulphate transporters have been isolated from a numb er of plant species. The transporters encoded by these genes are related to the major facilitator superfamily of proteins. They are predicted to conta in 12 membrane-spanning domains and function as H+/H2PO4- or H+/SO42- cotra nsporters. 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 regula ted by signals that respond to the nutrient status of the plant. Nutrient d emand and the availability of precursors needed in the assimilatory pathway s also regulate transcription of some of these genes. Information on the ce ll types in which phosphate and sulphate transporters are expressed is beco ming available. These data, together with functional characterisation of th e transporters, are enabling the roles of various transporters in the overa ll phosphate and sulphate nutrition of plants to be defined. (C) 2000 Elsev ier Science B.V. All rights reserved.