'Omics' and chemical approaches used to monitor iron-deficiency in citrus rootstocks

Two different 'omics' approaches were performed to a better comprehension of biological mechanisms involved in citrus iron (Fe) deficiency. Tips roots from Swingle citrumelo and Carrizo citrange (sensitive and tolerant rootstocks, respectively), growing in pots with control and chlorotic soil, were used for transcriptomic and proteomic analysis. CombiMatrix array was performed to isolate differential genes, among which glutathione peroxidase (GPX), SAUR gene and glutamate dehydrogenase (GDH) showed to be the most involved ones. They were switched on Swingle grown on calcareous conditions compared to Carrizo (in the same soil) and to the same stock in the control soil. The over-expression of GPX could be the effort of plants to neutralize the oxidative environment produced by stress. The involvement of auxin (and as consequence of SAUR gene) in the regulation of Fe deficiency responses is also well known. Both genes were considered in association to peroxidase, ferric chelate reductase activities, iron and chlorophyll content, to monitor the degree of suffering of rootstocks. Among differentially expressed proteins, identified by means of 2D-PAGE and RP-HPLC/nESI-MSMS, a strong down-regulation of cytosolic pyrophosphate-dependent phosphofructokinase β-subunit and NADPH-isocitrate dehydrogenase could produce plant inability to sustain the energetic request of cell roots.