Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/26/2008
Publication Date: 6/22/2008
Citation: Hernandez, G., Valdes-Lopez, O., Ramirez, M., Lara, M., Vance, C.P., Girard, L., Sanchez, F., Reyes, J.L. 2008. Essential role of MYB transcription factor PvPHR1 in phosphate starvation signaling in common bean (Phaseolus vulgaris) [abstract]. American Society of Plant Biologists Annual Meeting, Pan American Congress on Plants and BioEnergy, June 22-25, 2008, Merida, Mexico. Abstract No. P10012. Available: http://abstracts.aspb.org/pb2008/public/P10/P10012.html. Interpretive Summary:
Technical Abstract: Phosphorus (P), an essential element for plants, is one of the most limiting nutrients for plant growth. In Arabidopsis, several responses to P starvation (-P) are regulated at the level of transcription, involving transcription factors (TF) such as: PHR1, WRKY75, ZAT6, and BHLH. Despite the agronomic importance of legumes, little is known about their regulation of -P responses. Crop production of common bean (Phaseolus vulgaris), the most important legume for human consumption, is often limited by low P in the soil. In order to study P starvation signaling in beans, expression of MYB TF genes that were induced in -P bean roots was analyzed in detail. In particular we analyzed MYB TF TC2883 (PvPHR1), which was induced 2-fold and showed 63% identity to the Arabidopsis PHR1 gene. In order to investigate the possible role of PvPHR1, a RNAi approach was used to down-regulate this gene in composite bean plants. Target genes transcription analysis in -P composite bean plants indicated that PvPHR1 TF is an essential positive regulator for P acquisition, homeostasis and transport genes but not for phytohormone-metabolism genes involved in modification of root architecture. We identified bean genes homologous to Arabidopsis At4 (CV536419) and PHO2 (TC1095) that participate in the PHR1-mediated signal transduction pathway. In addition, a micro RNA homologous to Arabidopsis miR399 was cloned from beans. We showed, for the first time in a legume plant, that PvmiR399 transcription by PvPHR1 increases in -P bean plants. The analysis of P-deficient DCL1-silenced composite bean plants, that showed reduced PvmiR399 levels, lead us to conclude that PvmiR399 negatively modulates the regulation of PvPHO2 of -P target genes. A model for PHR1-mediated signaling pathway in beans is proposed.