Genetic manipulation of a high-affinity PHR1 target cis-element to improve phosphorous uptake in Oryza sativa L.

Abstract

Phosphorus (P) is an essential macronutrient for crop development and production. Phosphate starvation response 1 (PHR1) acts as the central regulator for Pi-signaling and Pi-homeostasis in plants by binding to the cis-element PHR1 binding sequence (P1BS; GNATATNC). However, how phosphate starvation-induced gene expression is regulated remains obscure. In this work, we investigated the DNA binding affinity of the PHR1 ortholog OsPHR2 to its downstream target genes in Oryza sativa (rice). We confirmed that a combination of P1BS and P1BS-like motifs are essential for stable binding by OsPHR2. Furthermore, we report that variations in P1BS motif bases affected the binding affinity of OsPHR2 and that the highest affinity motif was GaATATtC (designated the A-T-type P1BS). We also found that a combination of two A-T-type P1BS elements in tandem, namely HA-P1BS, was very efficient for binding of OsPHR2. Using the cis-regulator HA-P1BS, we modified the promoters of Transporter Traffic Facilitator 1 (PHF1), a key factor controlling endoplasmic reticulum-exit of phosphate transporters to the plasma membrane, for efficient uptake of phosphorous in an energetically neutral way. Transgenic plants with the modified promoters showed significantly enhanced tolerance to low phosphate stress in both solution and soil conditions, which provides a new strategy for crop improvement to enhance tolerance of nutrient deficiency.

Integrative Comparison of the Role of the PHOSPHATE RESPONSE1 Subfamily in Phosphate Signaling and Homeostasis in Rice

“…In this study, OsPHR proteins exhibited different P1BS binding affinities (Fig. 7), and their binding abilities were affected by variant bases in P1BS as reported by Ruan et al (2015). How the P1BS variant bases influence these affinities will be a subject of another study.…”

Complex Regulation of Plant Phosphate Transporters and the Gap between Molecular Mechanisms and Practical Application: What Is Missing?

“…This strategy has recently been proved to be feasible. Ruan et al (2015) demonstrated that the AT-type-P1BS (GaATATtC) has the highest affinity for OsPHR2. Overexpression of OsPHF1 driven by its native promoter, in which the P1BS and P1BS-like cis-elements are substituted with the AT-type-P1BS, leads to enhanced tolerance to low Pi stress under both solution and soil conditions (Ruan et al, 2015).…”

Analysis of EF-Hand Proteins in Soybean Genome Suggests Their Potential Roles in Environmental and Nutritional Stress Signaling

“…Here we surveyed the presence of eight classes of cis -elements (Supplemental Table S8) related to hormonal signal and/or stress responses, in the -1500 bp promoter regions upstream to the predicted transcription start sites of these EF-hand genes (Williams et al, 1992; Abe et al, 1997; Ulmasov et al, 1997; Fujimoto et al, 2000; Sakuma et al, 2002; Yang and Poovaiah, 2002; Osakabe et al, 2014; Ruan et al, 2015). Of these 262 EF-hand genes, 39 contain dehydration- and cold-responsive element DRE/CRT, 78 contain ABA-responsive element ABRE, 112 contain auxin-responsive element AuxRE, 17 contain ethylene-responsive element GCC-box, 45 contain environmental response-related element G-box, 81 contain signal response-related element CG-box, 28 contain drought and ABA signaling-related element MYB2-BS, and 66 contain phosphate starvation response-related element P1BS (Supplemental Table S9).…”