Zinc deficiency up-regulates expression of high-affinity phosphate transporter genes in both phosphate-sufficient and -deficient barley roots

Phosphate (P) is taken up by plants through high-affinity P transporter pro teins embedded in the plasma membrane of certain cell types in plant roots. Expression of the genes that encode these transporters responds to the P s tatus of the plants, and their transcription is normally tightly controlled . However, this tight control of P uptake is lost under Zn deficiency, lead ing to very high accumulation of P in plants. We examined the effect of pla nt Zn status on the expression of the genes encoding the HVPT1 and HVPT2 hi gh-affinity P transporters in barley (Hordeum vulgare L. cv Weeah) roots. T he results show that the expression of these genes is intimately linked to the Zn status of the plants. Zn deficiency induced the expression of genes encoding these P transporters in plants grown in either P-sufficient or -de ficient conditions. Moreover, the role of Zn in the regulation of these gen es is specific in that it cannot be replaced by manganese (a divalent catio n similar to Zn). It appears that Zn plays a specific role in the signal tr ansduction pathway responsible for the regulation of genes encoding high-af finity P transporters in plant roots. The significance of Zn involvement in the regulation of genes involved in P uptake is discussed.