Sources and availability of copper and Iron affect growth and development of crops

Iron (Fe) is a transition metal that is required by plants for its fundamental roles in cell redox chemistry. Iron is crucial in the active sites of numerous enzymes involved in processes such as mitochondrial respiration, photosynthesis, oxidative stress protection, and various metabolic pathways. Under Fe-deficiency conditions, chloroplast development and chlorophyll biosynthesis are impaired, resulting in the typical symptom of interveinal leaf chlorosis, so-called iron chlorosis. Copper (Cu) was first identify as a plant nutrient in the 1930s and, like Fe, it is a transition metal that participates to oxido-reductive reactions in plants of considerable biological. Typical symptoms of Cu shortage include stunted growth, leaf deformation, necrosis of apical meristems. Copper deficiency occurs on calcareous soils, in which Cu availability is low due to its insolubility at high pH or in soils with a high content of organic matter, due to the high affinity of Cu to organic compounds. Plant phenotypes associated with Cu toxicity share similarities with those related to Fe-deficiency, such as the presence of leaf chlorosis, decreased leaf chlorophyll content and enhanced oxidative stress. For several metabolic functions, organisms may alternatively use Fe or Cu-containing protein. The reason could be related to changes across the geological eras in the concentration of soluble transition metals in the biosphere along the increase of O2 content within the atmosphere. In order to overcome Fe limitation, plants have evolved two mechanisms to acquire Fe from sparingly available Fe sources. Non-graminaceous plants have a reduction-based mechanism, so called Strategy I, which involves the solubilization of ferric Fe via protons released into the rhizosphere, followed by reduction of Fe (III) by FRO2 reductases. and then the transport by IRT1. Several studies hypothesized that plantelectron-transport systems could reduce Fe3+ to Fe2+and also Cu2+ to Cu+. In response to Fe deficiency, grass plants activate the so-called Strategy II, that is based on the increase of biosynthesis and release of phytosiderophores (PS) in the rhizosphere. Plants could relisted also organic compound (organic acid) which could bound metal species in the soil solution. PSs and organic compounds release occurs also under Cu deficiency. The common and specific aspects of Fe and Cu acquisition mechanisms in plants is a topic of great interest, however little is known about the crosstalk of these two microelements and their reciprocal interaction or antagonism, especially at molecular level. This PhD thesis investigates the interactions between Cu and Fe acquisition in plants with the purpose to understand if their status and supply in different forms and amounts could affect their mutual acquisition. For this pourpose maize (Zea mays, L.) tomato (Lycopersicon esculentum) and melon (Cucumis melon) were chosen as model plants. Firstly, Cu- and Fe-deficiency symptoms related with shoot-and root-morphological responses were investigated. Moreover, antioxidant enzymes activity (SODs, CAT, APX and POX) as well as nutrients content were evaluated in shoots and roots. Secondary, with the purpose to evaluate the availability of different Fe and Cu compounds, different sources of Fe and Cu were supplied to maize plants while the Fe and Cu deficiencies were studied in tomato. Finally, the interactions between Cu and Fe was carried on two melon genotypes (Edisto, as wild type, and fefe, a Fe-deficient unresponsive mutant) using the split roots technique with the purpose to investigate the local and systemic signals involved in the regulation of Cu and Fe uptake by Strategy I plants. Physiological evidence showed local response to Fe deficiency while molecular analysis showed a systemic regulation. Highlighting the need of researches on the post transcriptional aspects of the Fe and Cu acquisition and regulation.