Phosphate deprivation in maize: genetics and genomics.

Plants acquire phosphorus (P) from the soil in order to reach the intracellular concentrations necessary for growth and reproduction. To prevent P starvation, both monocotyledonous and dicotyledonous plants have evolved well-regulated systems for inorganic phosphate (Pi) scavenging, acquisition, and recycling. Phosphate starvation responses (PSR) in plants include release of organic acids and hydrolytic enzymes to scavenge soil Pi from organic and inorganic sources, metabolic modifications to bypass ATP requirements, recycling andmobilization of internal P resources, modifications of root system architecture to increase soil exploratory capacity, and, for many plant species, the establishment of symbiotic relations with arbuscular mycorrhizal fungi (Bucher, 2007). Maize (Zea mays) is one of the most widely cultivated crop plants, for both staple food and industrial usage, in tropical and temperate soils worldwide. Under cultivation, especially in acidic and alkaline soils, large quantities of P fertilizer are applied to maize fields in order to maximize yields. P fertilizers, however, are becoming increasingly costly owing to dwindling natural reserves of rock Pi and an increase in the costs of extracting what remains; it is projected that we have already moved beyond the point of peak production (Cordell et al., 2011) and that reserves will be exhausted before the end of the century (Khasawneh et al., 1986). Recent progress in maize genetics and genomics has furthered characterization of the molecular basis of maize PSR, with the potential to provide important information in the development of maize varieties with enhanced P use efficiency.