Expression analyses of three members of the AtPHO1 family reveal differential interactions between signaling pathways involved in phosphate deficiency and the responses to auxin, cytokinin, and abscisic acid
- 652 Downloads
The PHO1 protein is involved in loading inorganic phosphate (Pi) to the root xylem. Ten genes homologous to AtPHO1 are present in the Arabidopsis thaliana (L.) Heyn genome. From this gene family, transcript levels of only AtPHO1, AtPHO1;H1 and AtPHO1;H10 were increased by Pi-deficiency. While the up-regulation of AtPHO1;H1 and AtPHO1;H10 by Pi deficiency followed the same rapid kinetics and was dependent on the PHR1 transcription factor, phosphite only strongly suppressed the expression of AtPHO1;H1 and had a minor effect on AtPHO1;H10. Addition of sucrose was found to increase transcript levels of both AtPHO1 and AtPHO1;H1 in Pi-sufficient or Pi-deficient plants, but to suppress AtPHO1:H10 under the same conditions. Treatments of plants with auxin or cytokinin had contrasting effect depending on the gene and on the Pi status of the plants. Thus, while both hormones down-regulated expression of AtPHO1 independently of the plant Pi status, auxin and cytokinin up-regulated AtPHO1;H1 and AtPHO1;H10 expression in Pi-sufficient plants and down-regulated expression in Pi-deficient plants. Treatments with abscisic acid inhibited AtPHO1 and AtPHO1;H1 expression in both Pi-sufficient and Pi-deficient plants, but increased AtPHO1;H10 expression under the same conditions. The inhibition of expression by abscisic acid of AtPHO1 and AtPHO1;H1, and of the Pi-starvation responsive genes AtPHT1;1 and AtIPS1, was dependant on the ABI1 type 2C protein phosphatase. These results reveal that various levels of cross talk between the signal transduction pathways to Pi, sucrose and phytohormones are involved in the regulation of expression of the three AtPHO1 homologues.
KeywordsAbscisic acid Arabidopsis Auxin Cytokinin PHO1 Phosphate PHR1
Abscisic acid insensitive 1
Phosphate starvation response 1
Phosphate deficient 1
This research was funded, in part, from a FNS grant (3100A0-105874) to YP, as well as from the Herbette Foundation and the Etat de Vaud. The authors are grateful to Javier Paz-Ares (Centro Nacional de Biotecnologia, Madrid) for providing seeds of phr1 mutant and Hatem Rouached (University of Lausanne) for critical reading of the manuscript.
- Jain M, Poling MD, Karthikeyan AS, Blakeslee JJ, Peer WA, Titapiwatanakun B, Murphy AS, Raghothama KG (2007) Differential effects of sucrose and auxin on localized phosphate deficiency-induced modulation of different traits of root system architecture in Arabidopsis. Plant Physiol 144:232–247PubMedCrossRefGoogle Scholar
- Koornneef M, Jorna ML, Brinkhorst-van der Swan DLC, Karssen CM (1982) The isolation of abscisic acid (ABA) deficient mutants by selection of induced revertants in non-germinating gibberellin sensitive lines of Arabidopsis thaliana (L.) Heynh. Theor Appl Genet 61:385–393Google Scholar
- Lopez-Bucio J, Hernandez-Abreu E, Sanchez-Calderon L, Perez-Torres A, Rampey R, Bartel B, Herrera-Estrella L (2005) An auxin transport independent pathway is involved in phosphate stress-induced root architectural alterations in Arabidopsis. Identification of BIG as a mediator of auxin in pericycle cell activation. Plant Physiol 137:681–691PubMedCrossRefGoogle Scholar
- Misson J, Raghothama KG, Jain A, Jouhet J, Block MA, Bligny R, Ortet P, Creff A, Somerville S, Rolland N, Doumas P, Nacry P, Herrerra-Estrella L, Nussaume L, Thibaud MC (2005) A genome-wide transcriptional analysis using Arabidopsis thaliana Affymetrix gene chips determined plant responses to phosphate deprivation. Proc Natl Acad Sci USA 102:11934–11939PubMedCrossRefGoogle Scholar
- Poirier Y, Bucher M (2002) Phosphate transport and homeostasis in Arabidopsis. In: Somerville CR, Meyerowitz EM (eds) The Arabidopsis book. American Society of Plant Biologists, RockvilleGoogle Scholar
- Stefanovic A, Ribot C, Rouached H, Wang Y, Chong J, Belbahri L, Delessert S, Poirier Y (2007) Members of the PHO1 gene family show limited functional redundancy in phosphate transfer to the shoot, and are regulated by phosphate deficiency via distinct pathways. Plant J 50:982–994PubMedCrossRefGoogle Scholar
- Torrey JG (1976) Root hormones and plant growth. Annu Rev Plant Physiol Plant Mol Biol 27:435–459Google Scholar
- Watts S, Rodriguez J, Evans S, Davies W (1981) Roots and shoot growth of plants treated with abscisic acid. Ann Bot 47:595–602Google Scholar