|Reyes, Jose Luis|
Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2008
Publication Date: 12/1/2008
Publication URL: http://hdl.handle.net/10113/28995
Citation: Valdes-Lopez, O., Arenas-Huertero, C., Ramirez, M., Lara, M., Sanchez, F., Girard, L., Vance, C.P., Reyes, J., Hernandez, G. 2008. Essential Role of MYB Transcription Factor: PvPHR1 and microRNA: PvmiR399 in the Phosphorus-Deficiency Signalling in Common Bean Roots. Plant Cell and Environment. 31(12):1834-1843. Interpretive Summary: Phosphorus is the major limiting nutrient in many agricultural soils. Common bean (Phaseolus vulgaris) is a primary crop grown for protein consumption in many parts of the world but particularly in developing countries. Growth of common bean is frequently limited due to inadequate phosphorus. In efforts to understand how common bean growth adapts to low phosphorus, we identified thousands of genes that were expressed in common bean roots in phosphate-stressed conditions. One of the genes we identified is a gene involved in signaling to the plant that soil phosphorus is low. This gene is designated MYB. In this report we show that the MYB gene is essential for signaling to the plant that soil phosphorus is inadequate. We further show that if MYB gene expression is compromised, the common bean plant no longer can respond to low phosphorus. These results are important because modifying MYB gene expression through biotechnology may lead to improved crop growth under phosphorus limitations.
Technical Abstract: Phosphorus (P), an essential element for plants, is one of the most limiting nutrients for plant growth. Few transcription factor (TF) genes involved in P-starvation signaling have been characterized for Arabidopsis and rice, but none for legumes. Crop production of common bean (Phaseolus vulgaris), the most important legume for human consumption, is often limited by low P in the soil. Despite its agronomic importance, nothing is known about transcriptional regulation in P-deficient bean plants. We functionally characterized the P deficiency induced MYB TF (TC2883 (Dana Farber Cancer institute, Common Bean Gene Index), ortholog to AtPHR1 (PvPHR1). For its study we applied RNAi technology, used for the first time in bean composite plants. PvPHR1 is a positive regulator of genes implicated in P transport, remobilization, and homeostasis, but not of phytohormone related genes probably involved in the modification of root architecture. Though there are no reports on the regulatory roles of microRNAs (miRNA) in legumes, we demonstrated that PvmiR399 is an essential component of the PHR1 signaling pathway. The analysis of DICER-like 1 (PvDCL1) silenced bean composite plants suppressed for PvmiR399 accumulation, suggested that MiR399 is a negative regulator of the ubiquitin E2 conjugase: PvPHO2 expression. In turn, PvPHO2 regulates--directly or indirectly--the expression of some P responsive genes. Our results constitute the basis for understanding the signaling for P starvation responses in common bean and may contribute to crop improvement.