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Title: Identification of genes induced in proteoid roots of white lupin under nitrogen and phosphorus deprivation, with functional characterization of a formamidase

item RATH, MOUSUMI - California State University
item SALAS, JAY - California State University
item PARHY, BANDITA - California State University
item NORTON, ROBERT - California State University
item MENAKURU, HIMABINDU - California State University
item SOMMERHALTER, MONIKA - California State University
item HATLSTAD, GREG - University Of Minnesota
item KWON, JAIMYOUNG - California State University
item ALLAN, DEBORAH - University Of Minnesota
item Vance, Carroll
item UHDE-STONE, CLAUDIA - California State University

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/2010
Publication Date: 4/15/2010
Citation: Rath, M., Salas, J., Parhy, B., Norton, R., Menakuru, H., Sommerhalter, M., Hatlstad, G., Kwon, J., Allan, D.L., Vance, C.P., Uhde-Stone, C. 2010. Identification of genes induced in proteoid roots of white lupin under nitrogen and phosphorus deprivation, with functional characterization of a formamidase. Plant and Soil. 334(1-2):137-150.

Interpretive Summary: Phosphorus is a critical non-renewable nutrient for crop growth. In the next 30 years inexpensive sources of phosphorus fertilizer are projected to be depleted. A major objective for agriculture is to improve crop plant phosphorus acquisition and use. White lupin is an important crop throughout the world. It is well adapted to flourish on soils with low phosphorus. White lupin adaptation to low phosphorus is through the formation of numerous lateral roots called cluster roots. Cluster roots increase the soil volume that can be explored by white lupin. In addition, numerous biochemical and molecular changes that contribute to phosphorus efficiency occur in white lupin roots growing under phosphorus stress. Much of the adaptation to phosphorus stress in white lupin involves carbon metabolism. In this study we isolated and characterized a formamidase gene involved in white lupin root carbon metabolism. The gene is highly expressed under both phosphorus and iron deficiency. We also studied the physical and catalytic properties of the formamidase enzyme. We postulate that the formamidase gene is supplying one carbon molecule to metabolic pathways involved in adaptation to phosphorus deficiency.

Technical Abstract: White lupin (Lupinus albus L.) is considered a model system for understanding plant acclimation to nutrient deficiency. It acclimates to phosphorus (P) and iron (Fe) deficiency by the development of short, densely clustered lateral roots called proteoid (or cluster) roots; proteoid-root development is further influenced by nitrogen (N) supply. In an effort to better understand proteoid root function under various nutrient deficiencies, we used nylon filter arrays to analyze 2,102 expressed sequence tags (ESTs) from proteoid roots of P-deficient white lupin. These have been previously analyzed for up-regulation in –P proteoid roots, and were here analyzed for up-regulation in proteoid roots of N-deprived plants. We identified a total of 19 genes that displayed up-regulation in proteoid roots under both P and N deprivation. One of these genes showed homology to putative formamidases. The corresponding open reading frame was cloned, overexpressed in E. coli, and the encoded protein was purified; functional characterization of the recombinant protein confirmed formamidase activity. Though many homologues of bacterial and fungal formamidases have been identified in plants, to our knowledge, this is the first report of a functional characterization of a plant formamidase.