Root protein profiles of two citrus rootstocks grown under iron sufficiency/deficiency conditions

Two citrus rootstocks, one sensitive to iron deficiency [Swingle Citrumelo (SC)] and the other tolerant [Carrizo Citrange, (CC)], were studied to characterize variation in their root protein profile induced by iron-deficient conditions. Plants of both rootstocks were grown in two different soils, one volcanic (v) and the other calcareous (c), containing 0% and 10% active lime, respectively. To evaluate the effects of the calcareous soil on the protein accumulation of both rootstocks, the root protein profiles (SCc vs SCv and CCc vs CCv) were characterized by two-dimensional gel electrophoresis, thus obtaining, for the first time, a reference map of this previously uncharacterized proteome. A total of 219 spots, significantly changed in abundance, were analyzed by high-performance liquid chromatography nano electrospray ionization tandem mass spectrometry. The identified proteins were classified according to their putative function and known biosynthetic pathways. Principal component analysis, comparing the four sets of data, indicated that each group clustered together with low variance and that CCv and CCc data sets were well differentiated, whereas SCv and SCc were similar.