Modulating Nitrogen Flux in Sorghum and Wheat

Nitrogen assimilation and remobilization is essential in plant growth and development. To maximize crop yield and plant productivity large amounts of nitrogenous fertilizers are often applied to fields. Modulating nitrogen flux to improve nitrogen use efficiency (NUE) would not only reduce input costs but also help mitigate pollution of aquatic ecosystems by the reduction of fertilizer inputs. As a means to perturb nitrogen flux in sorghum (Sorghum bicolor (L.) Moench) and wheat (Triticum aestivum L.), we have developed a set of transgenic events via Agrobacterium tumefaciens-mediated transformation. This set includes expression cassettes that harbor (i) a barley alanine amino transferase (HvALA-AT), driven by either a rice tissue specific promoter (OsAnt1) or the sugarcane UBI4 promoter; (ii) a rice cytosolic glutamate synthetase (OsGS1) driven by the sugarcane UBI4 promoter; (iii) a rice glutamate synthase (OsGOGAT) driven by the sugarcane UBI4 promoter; and (iv) a maiz DOF1 transcription factor driven by either UBI4 promoter or the maize rbcS1 promoter. Preliminary characterization of progeny derived from these expression cassettes in both sorghum and wheat will be presented. Our short-term goal is to identify lead events based on greenhouse phenotype studies for use in down-stream field evaluations.