Aim of the present work was to investigate the involvement of plasma membrane (PM) H(+)-ATPase (E.C. 3.6.3.6) isoforms of cucumber (Cucumis sativus L.) in the response to Fe deficiency. Two PM H(+)-ATPase cDNAs (CsHA1 and CsHA2) were isolated from cucumber and their expression analysed as a function of Fe nutritional status. Semi-quantitative reverse transcriptase (RT)-PCR and quantitative real-time RT-PCR revealed in Fe-deficient roots an enhanced accumulation of CsHA1 gene transcripts, which were hardly detectable in leaves. Supply of iron to deficient plants caused a decrease in the transcript level of CsHA1. In contrast, CsHA2 transcripts, detected both in roots and leaves, appeared to be unaffected by Fe. This work shows for the first time that a transcriptional regulation of PM H(+)-ATPase involving a specific isoform occurs in the response to Fe deficiency.