CHANGES IN THE PROTEOMIC AND METABOLOMIC PROFILES OF BETA VULGARIS ROOT TIPS IN RESPONSE TO IRON DEFICIENCY AND RESUPPLY
A comprehensive analysis of the proteomic and metabolomic changes occurring in sugar beet root tips under Fe deficiency and Fe resupply has been carried out. Root tip samples were taken from Fe-sufficient (+Fe), Fe-deficient (-Fe) and Fe-resupplied plants at 24 and 72 h (in the latter case in two different root zones). Proteome maps were obtained using two-dimensional IEF-SDS PAGE. More than 140 spots were detected in gels from root tips of Fe-deficient and control plants, and Fe deficiency induced significant changes in the intensity of a large number of these polypeptides, many of them related to carbohydrate catabolism. A protein not present in Fe-sufficient roots, DMRL synthase, was present in high amounts in root tips from Fe-deficient sugar beet plants and was also found to be transcriptionally regulated by Fe status. Seventy-seven metabolites were identified by GC-MS. Statistical analysis using univariate, breakdown one-way ANOVA, and multivariate, supervised partial least square was carried out. Score scatter plots using the first 2 components showed a good separation of the different treatments, with metabolites in the 72 h Fe-resupplied samples being close those obtained in Fe-sufficient conditions. An activation of TCA cycle components was observed in Fe-deficient root tips when compared to the controls. An increase in the amount of the raffinose series of oligosaccharides (RSOs), including raffinose, galactinol, lacto-bionic acid and myo-inositol was observed in root tips of Fe-deficient and 24 h Fe-resupplied plants when compared to the controls.