Understanding Plant Response to Nitrogen Limitation and Identification of Genes for Improving Crop Nitrogen Use Efficiency

Development of genetic varieties with improved nitrogen use efficiency (NUE) is essential for sustainable agriculture. To achieve that, it is important to understand how plants respond to N stress. We have been using the model plant Arabidopsis to discover genes involved in regulating the N limitation response as well as genes important for improving NUE. Also, efforts have been directed towards understanding the molecular basis of plant responses to N by whole genome transcriptional profiling both in Arabidopsis and rice. One approach has been adapted to identify genes for improving crop NUE is through transcriptional profiling. One such example is a rice early nodulin gene OsENOD93-1, which responded significantly to both N induction and N reduction but with unknown function when selected. Transgenic rice plants over-expressing OsENOD93-1  had increased shoot dry biomass and seed yield, demonstrating that transcriptional profiling, coupled with a transgenic validation approach, is an effective strategy for gene discovery. Another approach used to identify genes for improving crop NUE is through the knowledge gained from the study on model plant Arabidopsis. One such example is the OsGATA16 gene, the rice orthologue gene of Arabidopsis GNC, which positively regulates the level of chlorophyll. This information has been used to generate transgenic corn lines and these are being tested under different N conditions.