Poster: Environmental Physiology

Abs # P03015: Chronic and transient effects of nitrogen saturation on root processes in a dominant prairie grass Andropogon gerardii: Linking gene expression profiles and ecological responses

Presenter:	Surabhi, Giridara-Kumar       Contact Presenter
Authors	Surabhi, Giridara-Kumar   (A)   Sanjay, Kumar  (A)   Alam, Nausheen   (A)   Caragea, Doina   (B) (C)  Lu, Nanyan  (C)   Hurt, Amy  (A)   Loretta , Johnson  (A)   Shah, Jyoti   (D)
Affiliations:	(A): Division of Biology and Ecological Genomics Institute, Kansas State University (B): Department of Computing and Information Sciences, Kansas State University (C): Bioinformatics Center, Kansas State University (D): Department of Biological Sciences, University of North Texas

Tallgrass prairie is amongst the most productive grasslands. In spite of the importance of roots in grazed and burned prairie, effects of nitrogen (N) on roots remain poorly understood. Our goal is to understand the genomic, molecular and physiological response of roots of big bluestem (Andropogon gerardii), the dominant grass, to changes in the availability of N. We assess responses to changes in N using long and short term plots at Konza Prairie, KS. Plots have been chronically treated for 6 yr with 4 levels of N (0, 2.5, 5 and 10gN/m²/yr) and a parallel set of plots have been treated only once. This design allows us to identify transient and chronic effects and to detect thresholds of response. We used cross-species microarrays by hybridizing cDNA from big bluestem roots to Zea mays oligonucleotide arrays to identify genes that are differentially expressed in response to N. 596 genes showed statistically significant differential expression with chronic high N. Genes that were down regulated include those coding for transcription factors (MADS-box), transporters of nitrate and iron, and growth regulators. Genes that were up regulated include those involved in defense/stress response, and signaling. 569 genes showed statistically significant differential gene expression under short-term high N. Up regulated genes include those important in N metabolism (GS) and antioxidative metabolism (GPX, GST). Down regulated genes include those involved in regulating carbohydrate and N metabolism (14-3-3), transporters (sugar, ankyrin-kinase), and growth regulation (auxin). We are exploring the possibility of detecting early signs of N saturation through gene expression profiles of roots, and linking ecological responses to gene functions under natural environment.