Over-expression of a high-affinity phosphate transporter in transgenic barley plants does not enhance phosphate uptake rates

Authors:
  • JJJanine M. Jarmey
    Janine M. Jarmey
  • SMStephen R. Mudge
    Stephen R. Mudge
  • FSFrank W. Smith
    Frank W. Smith
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Abstract
Transgenic barley plants that over-express the gene encoding a phosphate transporter were generated and used to test the hypothesis that manipulation of transporters may lead to improved phosphate uptake by plant roots. Replicate T2 seedlings from a homozygous line with a single locus insertion were grown in dilute flow culture. The phosphate contents and uptake rates of these plants were compared with control transgenic and wild-type plants. When external phosphate concentration was maintained at 10 µM, all plants including the transgenic over-expressing line displayed low rates of phosphate uptake and contained high levels of phosphate in the shoot tissue. When external phosphate concentration was maintained at 2 µM, the uptake rates increased to a similar level in all plant lines. Three transgenic over-expressing lines were then grown in soil at a range of phosphate concentrations and the dry weights and total phosphorus contents of the shoots were measured and compared to a transgenic control line. The results showed that over-expression of the gene encoding a phosphate transporter did not improve the uptake of phosphate under any of the conditions tested. Transporter activity is likely to be influenced by post-transcriptional mechanisms and will require further investigation before this strategy can be applied to improving plant nutrition.