Alternation of plasma membrane H+-ATPase in cucumber roots under different iron nutrition

The strategy I developed by dicotyledonous plants to efficiently acquire of iron involve the action of proton-extruding H+-ATPases. These proteins are responsible for the solubilization of iron through rhizosphere acidification. Previously, it has been documented that acidification of the rhizosphere involve specific isoforms of plasma membrane proton pumps in response to Fe deficiency in dicot plants such as Arabidopsis, Cucumis sativus, Lycopersicon and Pisum sativum. In this work, we have investigated the effect of Fe nutritional status on the activity of plasma membrane H+-ATPases at the level of transcription, protein accumulation and post-translational modification. Two genes (CsHA2 and CsHA3) were isolated from different parts of cucumber and their expression analyzed under different Fe treatments (0, 25 and 80 μM Fe). Transcript level of CsHA2 was detected in both vegetative organs (roots and cotyledons), while CsHA3 expression was limited only to the roots in immature plants. These two genes were up-regulated under Fe deficiency in cucumber roots and their expression was decreased in the presence of 80 μM Fe. We have shown that the post-translational modification of protein via phosphorylation and its accumulation as a target of activation in Fe-deficient plants might not be responsible for the increase in the H+-ATPase activity.