Knock out of the PHOSPHATE 2 Gene TaPHO2-A1 Improves Phosphorus Uptake and Grain Yield under Low Phosphorus Conditions in Common Wheat.

Xiang Ouyang,Yiping Tong,Xueqiang Zhao,Wan Teng,Xia Hong,Wei Zhang,Xue He,Wenying Ma

doi:10.1038/srep29850

Abstract

MiR399 and its target PHOSPHATE2 (PHO2) play pivotal roles in phosphate signaling in plants. Loss of function mutation in PHO2 leads to excessive Pi accumulation in shoots and growth retardation in diploid plants like Arabidopsis thaliana and rice (Oryza sativa). Here we isolated three PHO2 homologous genes TaPHO2-A1, -B1 and -D1 from hexaploid wheat (Triticum aestivum). These TaPHO2 genes all contained miR399-binding sites and were able to be degraded by tae-miR399. TaPHO2-D1 was expressed much more abundantly than TaPHO2-A1 and -B1. The ion beam-induced deletion mutants were used to analyze the effects of TaPHO2s on phosphorus uptake and plant growth. The tapho2-a1, tapho2-b1 and tapho2-d1 mutants all had significant higher leaf Pi concentrations than did the wild type, with tapho2-d1 having the strongest effect, and tapho2-b1 the weakest. Two consecutive field experiments showed that knocking out TaPHO2-D1 reduced plant height and grain yield under both low and high phosphorus conditions. However, knocking out TaPHO2-A1 significantly increased phosphorus uptake and grain yield under low phosphorus conditions, with no adverse effect on grain yield under high phosphorus conditions. Our results indicated that TaPHO2s involved in phosphorus uptake and translocation, and molecular engineering TaPHO2 shows potential in improving wheat yield with less phosphorus fertilizer.

Highlights

Plants have evolved complicated physiological and biochemical responses to adapt to the limiting P conditions
Under high P conditions, the tapho2-a1 mutant had significantly higher SDW (Fig. 4c) and lower root/shoot ratio (Fig. 4e) than did the wild type, and tapho2-b1 mutant had longer primary root length (Fig. 4f) than did the wild type. Under both low P and high P conditions, the tapho2-d1 mutant had significantly lower SDW, RDW, root/shoot ratio and shorter primary root length than did the wild type (Fig. 4c–f). These results suggested that the seedlings of the tapho2-a1 and tapho2-b1 mutants had advanced adaptive capacity to Pi-deficiency conditions, while significant repression of plant growth occurred in the seedlings of tapho2-d1 mutant under both low P and high P conditions when the plants were grown in nutrient solution
The crucial roles of Phosphate 2 (PHO2) in regulating Pi signaling have been elaborately depicted in Arabidopsis and rice, and PHO2 exists in single copy in these diploid plant species[12,13,16]

Summary

Introduction

Plants have evolved complicated physiological and biochemical responses to adapt to the limiting P conditions. Overexpression of PHR1 and its homologs activates the expression of many PSI genes including Pi transporters, Phosphate Starvation[1] (IPS1) and miR399, and leads to excessive Pi accumulation in shoots of Arabidopsis, rice and wheat (Triticum aestivum)[5,6,7,8,9,10]. By comparing the transcriptome profiles of wheat and rice, an IPS1-mediated signaling cascade (include PHR1-IPS1-miR399-PHO2) and its downstream functions involved in a general response to Pi starvation were revealed[27]. Field experiments exhibited that the tapho2-a1 mutant displayed higher aerial P accumulation and grain yield than did the wild type under low P conditions These results indicated that TaPHO2 involved in Pi signaling and showed potential in improving PUE and yield in wheat

Methods

Results

Conclusion