Physiological and transcriptomic characterization of white lupin response to Fe deficiency

Iron (Fe) and phosphorus (P) are essential nutrients for plants growth. Despite their abundance in soils, they are barely available for plants. In order to overcome these nutritional stresses, plants have evolved strategies including physiological, biochemical and morphological adaptations. Biosynthesis and release of low molecular weight compounds from the roots play a crucial role in P and Fe mobilization. White lupin (Lupinus albus L.) is considered a model plant for studying root exudates and for P-deficient adaptation. White lupin is able to markedly modify its root architecture by forming special structures called cluster roots, and modifies the rhizospheric soil characteristics by biosynthesising and releasing great amounts of exudates. These phenomena are quite well described in response to P deficiency, but there is few information on the adaptation of a cluster-root producing plant species to Fe deficiency. This prompted this work, aimed to characterize the physiological and transcriptomic responses of white lupin plants to Fe deficiency. Occurrence of Strategy I components and interactions with P nutrition has been also investigated in this work. Results showed a physiological and transcriptional link between the responses to Fe and P deficiency in white lupin roots. Phosphorus-deficient plants activated the Strategy I Fe acquisition mechanisms that lead to an enhanced Fe mobilization and translocation and that might help the P acquisition process. On the other hand, also the Fe deficiency enhanced the phosphate acquisition and some P-deficient-responsive genes were overexpressed. RNA of Roots of Control Plants, Root Apices of Fe Deprived Roots, Root Clusters of Fe Deprived Roots and Root Clusters of P Deprived Roots were sequenced in triplicate on an Illimina HiSeq2000 Sequencer