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.

Coexpression-Based Clustering of Arabidopsis Root Genes Predicts Functional Modules in Early Phosphate Deficiency Signaling

“…The Myb-type transcription factor PHOSPHATE STARVATION RESPONSE1 (PHR1) is a conserved key regulator, directly controlling a subset of Pi deficiency genes by binding to an imperfect palindromic sequence motif and thereby activating these genes (Rubio et al, 2001). Consistent with a critical regulatory role, overexpression of PHR1 led to increased Pi accumulation (Nilsson et al, 2007). The activity of PHR1 is controlled by the SUMO E3 protein ligase SIZ1 (Miura et al, 2005), representing the most upstream component of the Pi deficiency signaling cascade identified thus far.…”

Biotechnology of nutrient uptake and assimilation in plants

“…2). In Arabidopsis, overexpression of PHOSPHATE STARVATION RESPONSE1 (PHR1), a master TF controlling a large subset of Pi stressresponsive genes, including PHT genes, resulted in a 2.5-and 4-fold increase in shoot Pi accumulation, under Pi-sufficient and Pi-stress conditions, respectively (Nilsson et al, 2007). Such increases have been associated directly with increased transcript levels of AtPHT1;7, AtPHT1;8, and AtPHT1;9, confirming that Pi acquisition is a concerted action between several transporters and that their individual overexpression might not be sufficient to have a significant impact on Pi content and plant growth.…”

Update on White Lupin Cluster Root Acclimation to Phosphorus Deficiency Update on Lupin Cluster Roots

“…The classic example of transcriptional regulation of P-responsive genes was delineated through studies of the MYB coiled-coil TF phosphate starvation response gene PHR1 (Rubio et al, 2001;Miura et al, 2005;Nilsson et al, 2007;. Rubio et al (2001) identified an Arabidopsis mutant, phr1, that when grown under P deficiency had reduced accumulation of anthocyanin and defective expression of P deficiency response genes.…”