Analysis of nitrogen use efficient rice over-expressing a barley alanine aminotransferase

Nitrogen (N) is a crucial plant nutrient that farmers tend to apply to their crops in excess in order to gain high yields. However, crop plants are generally inefficient at N uptake from the soil, much of the applied N fertilizers are lost to the plant through leaching, volatization and by microbial action. It is important to breed and/or design nitrogen use efficient (NUE) crop plants that can produce the same, or higher yields with less applied N fertilizer. Growth of NUE crops, coupled with implementation of best fertilizer management practices, would reduce the need for N fertilizer application, reducing both costs to the farmer and environmental pollution. We have recently genetically engineered rice (Oryza sativa L.) by introducing a barley alanine aminotransferase (AlaAT) cDNA driven by a rice tissue specific promoter (Shrawat et. al., 2008). The transgenic rice showed significantly increased biomass and grain yield compared to control plants when grown at a fixed, high amount of ammonium. We also analysed the transcriptomic profile of these transgenic plants using Affymetrix Rice GeneChip microarrays (Beatty et al., 2009). In the current study, we compared various physiological and genetic data from alanine aminotransferase over-expressing transgenic plants to control plants grown at three different nitrogen levels and demonstrated significant changes between them. Our studies demonstrate that the manipulation of AlaAT can be affected by the level of available nitrogen. In addition, certain transcripts in the transgenic lines can be influenced by nitrogen levels as well.