Selenium (Se) is an essential element for animals. In humans, low dietary Se intakes are associated with health disorders including oxidative stress-related conditions, reduced fertility and immune functions and an increased risk of cancers. Wheat is one of the most important Se sources for the human diet, and a decline in dietary Se intake in the UK has been attributed to a change in the source of wheat flour for bread-making from North America to Europe. Breeding strategies for improved Se accumulation will benefit from an understanding of the mechanisms of Se uptake and the potential for their genetic manipulation. Hypothetically, enhancing the expression of genes encoding Se transporters in wheat roots, and/or expressing alleles of Se transporters that catalyse faster Se transport across root cell membranes, could increase Se uptake capacity and Se accumulation. This project tests these hypotheses using the following approaches:

Sulphate transporters are undoubtedly responsible for selenate uptake. Sulphate and selenate compete for uptake, and as selenate is usually of low abundance, sulphate uptake dominates; this can be to the total exclusion of selenate uptake, resulting in a nutritionally suboptimal selenium content of crops. Small differences in the sequence and structure of a transporter can affect substrate specificity and identifying such variation in sulphate transporters will considerably enhance our knowledge of the functioning of these transporters. Understanding the molecular basis of sulphate/selenate discrimination may allow the selection of germplasm which could preferentially accumulate selenium even in a background of high sulphur fertility, or conversely, limiting selenate accumulation under circumstances of high selenium backgrounds.

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