Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2007
Publication Date: 4/20/2007
Citation: Hernandez, G., Ramirez, M., Valdes-Lopez, O., Gebeyaw, M.T., Graham, M.A., Czechowski, T., Schlereth, A., Wandrey, M., Erban, A., Cheung, F., Wu, H., Lara, M., Town, C.D., Kopka, J., Udvardi, M.K., Vance, C.P. 2007. Phosphorus stress in common bean: root transcript and metabolic responses. Plant Physiology. 144:752-767. Interpretive Summary: Common bean (Phaseolus vulgaris L.) is the world's most important grain legume for direct human consumption. Its growth, however, is frequently limited due to low phosphorus (P) availability in soil. In this report we use three research approaches to identify genes that may be important in helping beans and other crops to grow in P-deficient soils. In one series of experiments we measured the expression of some 2,200 genes in roots of P-sufficient and P-deficient bean plants. We found a large number of genes that were induced to greater activity by P-deficiency stress. In another approach we used a very sensitive method to measure the expression of 372 genes that are known to control the expression of other genes. We also measured metabolites that accumulate in P-deficient bean plants. Because the genes that we identified through large-scale expression and metabolite analysis of bean plants appear to be enhanced during P deficiency in several crop species, they may be excellent candidates for use as molecular markers for identifying and breeding better germplasm that tolerates low soil P conditions. They may also be useful as candidate genes to improve P tolerance through plant biotechnology.
Technical Abstract: Phosphorus (P) is an essential element for plant growth. Crop production of common bean (Phaseolus vulgaris), the most important legume for human consumption, is often limited by low P in the soil. Functional genomics technologies were used to investigate global gene expression and metabolic responses of bean plants grown for 3 weeks under P-deficient (-P) and P-sufficient conditions. As expected, P-starved plants showed enhanced dry weight root/shoot ratio as well as [MG1] reduced leaf area and net photosynthesis rates. Transcript profiling was performed through hybridization of nylon filter arrays spotted with cDNAs of 2,212 unigenes of –P root library. A total of 126 genes, representing different functional categories, showed significant differential expression in response to P: 62% of these were induced in -P roots. A set of 372 bean transcription factor (TF) genes, coding for proteins with InterPro domains characteristic or diagnostic for TF, were identified from The Institute of Genomic Research /Dana Farber Cancer Institute Common Bean Gene Index. Using real-time RT-PCR analysis, 17 TF genes were found to be differentially expressed in –P roots; 4 TF genes, including MYB TFs, were induced. Non-biased metabolite profiling using gas chromatography coupled to mass spectrometry was used to assess the degree to which changes in gene expression in –P roots affect overall metabolism. Stress related metabolites such as polyols accumulated in –P roots as well as sugars, which are known to be essential for P stress gene induction.