title: Increased expression of the MYB-related transcription factor, PHR1, leads to enhanced phosphate uptake in Arabidopsis thaliana.
abstract: Plants have evolved a number of adaptive strategies to cope with fluctuations in phosphorus (P) supply. The current knowledge of the transcriptional regulation of the P-starvation response in plants is limited. However, one MYB-related transcription factor, PHR1, is known to be involved in the P-starvation response. In this paper, we characterize a T-tagged phr1 knockout mutant and a series of transgenic plant lines which over-express PHR1 in wild type (WT) and phr1 mutant background. The knockout mutant has an altered phosphate (Pi) allocation between root and shoot; accumulates less anthocyanins, sugars and starch than P-starved WT; has a lower AGPase activity; and is impaired in induction of a subset of Pi starvation-induced genes. Expression of PHR1 in the phr1 mutant rescues the responsiveness to P-starvation and leads to WT levels of sugars and starch during Pi starvation conditions, confirming the involvement of PHR1 in adjusting carbon metabolism. Over-expression of PHR1 further resulted in a dramatic increase in the microRNA miR399d, and this resulted in changes in the transcript level for the target gene PHO2. Furthermore, over-expression of PHR1 in both WT and phr1 mutant results in strongly increased content of Pi irrespective of P regime. This shows that targeting a key regulatory element in the Pi starvation regulatory network represents a useful approach for molecular breeding of plants towards more efficient Pi uptake and assimilation.
authors.affiliation: Plant Biochemistry Laboratory, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
authors.forename: Lena
authors.initials: L
authors.lastname: Nilsson
authors.forename: Renate
authors.initials: R
authors.lastname: Müller
authors.forename: Tom Hamborg
authors.initials: TH
authors.lastname: Nielsen
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D050260:Carbohydrate Metabolism / Q000502:physiology*; D002244:Carbon / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D016254:Mutagenesis, Insertional; D010641:Phenotype; D010758:Phosphorus / Q000378:metabolism*; D018520:Plant Shoots / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C514695:PHR1 protein, Arabidopsis; D014157:Transcription Factors; D010758:Phosphorus; D002244:Carbon