Deciphering components of the nitrogen limitation response in arabidopsis

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Considerable stress will be placed on world-wide crop production due to an increased human population, an increase in the crops used per person and environmental issues. Besides water availability, nitrogen is the major limiting factor in crop production. To develop crops that can use nitrogen more efficiently, we must understand the role of genotype on its acquisition and use. Therefore, it is essential to understand the role of signaling and regulatory mechanisms that control nitrogen metabolism under nitrogen limitation conditions. In this proposal, the studies will focus on molecular genetic and genomic studies in Arabidopsis. First, we wish to understand in much greater detail how a plant senses nitrogen limitation. Second, we wish to target a set of transcription factors (GNC and CGA-1) for which we have considerable evidence for their role in controlling the carbon-nitrogen balance under nitrogen limitation. Further, over-expression of these genes can lead to an enhanced growth phenotype in Arabidopsis and rice. We identified the nitrogen limitation adaptability (nla) gene as a key component for the adaptation of Arabidopsis plant grown under limited nitrogen conditions. We will use a variety of techniques including genetic, biochemical and physiological approaches to identify additional genes that are essential for the nitrogen limitation adaptability pathway. In addition, we will delineate the targets of GNC and CGA-1 transcription factors that will allow us to further understand their roles. Finally, we will do a metabolome and transcriptome analysis of the response of Arabidopsis to limiting nitrogen both in wild-type and in the various mutant and over-expression lines that we have developed or will develop in the future. The long term goal is to use this information to target genes in crop plants to develop genetic lines that yield better under field conditions where less nitrogen fertilizer is used. This, in turn, would significantly improve both the economic and environmental sustainability of crop production.