Arabidopsis Pht1;5 Mobilizes Phosphate between Source and Sink Organs and Influences the Interaction between Phosphate Homeostasis and Ethylene Signaling

Vinay K Nagarajan,Ajay Jain,Aaron P Smith,Kashchandra G Raghothama,Anthony J Lewis,Michael D Poling

doi:10.1104/pp.111.174805

Abstract

Phosphorus (P) remobilization in plants is required for continuous growth and development. The Arabidopsis (Arabidopsis thaliana) inorganic phosphate (Pi) transporter Pht1;5 has been implicated in mobilizing stored Pi out of older leaves. In this study, we used a reverse genetics approach to study the role of Pht1;5 in Pi homeostasis. Under low-Pi conditions, Pht1;5 loss of function (pht1;5-1) resulted in reduced P allocation to shoots and elevated transcript levels for several Pi starvation-response genes. Under Pi-replete conditions, pht1;5-1 had higher shoot P content compared with the wild type but had reduced P content in roots. Constitutive overexpression of Pht1;5 had the opposite effect on P distribution: namely, lower P levels in shoots compared with the wild type but higher P content in roots. Pht1;5 overexpression also resulted in altered Pi remobilization, as evidenced by a greater than 2-fold increase in the accumulation of Pi in siliques, premature senescence, and an increase in transcript levels of genes involved in Pi scavenging. Furthermore, Pht1;5 overexpressors exhibited increased root hair formation and reduced primary root growth that could be rescued by the application of silver nitrate (ethylene perception inhibitor) or aminoethoxyvinylglycine (ethylene biosynthesis inhibitor), respectively. Together, these data indicate that Pht1;5 plays a critical role in mobilizing Pi from P source to sink organs in accordance with developmental cues and P status. The study also provides evidence for a link between Pi and ethylene signaling pathways.

Highlights

Phosphorus (P) remobilization in plants is required for continuous growth and development
In Arabidopsis (Arabidopsis thaliana), there are nine such PHOSPHATE TRANSPORTER1 (Pht1) proteins with 60% to 95% sequence similarity, and their homologs have been identified in several crop species
[pht1;5-1] and SALK_138009C [pht1;5-2]) were identified with T-DNAs inserted at 919 bp and 1,020 bp, respectively, downstream of the translation start site of the Pht1;5 gene (Fig. 1B)

Summary

Introduction

Phosphorus (P) remobilization in plants is required for continuous growth and development. Spatial expression patterns of Pht members in different tissue types and organs of Arabidopsis suggest their potential involvement in Pi acquisition and in internal Pi distribution to metabolically active and growing parts of the plant (Karthikeyan et al, 2002, 2009; Mudge et al, 2002; Miller et al, 2009). We provide evidence for a tangible link between Pi transporters and ethylene signaling

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Results

Conclusion