Functional Disruption of a Chloroplast Pseudouridine Synthase Desensitizes Arabidopsis Plants to Phosphate Starvation.

Shan Lu,Zai Zheng,Dong Liu,Chenyi Li,Ye Zhang

doi:10.3389/fpls.2017.01421

Abstract

Phosphate (Pi) deficiency is a common nutritional stress of plants in both agricultural and natural ecosystems. Plants respond to Pi starvation in the environment by triggering a suite of biochemical, physiological, and developmental changes that increase survival and growth. The key factors that determine plant sensitivity to Pi starvation, however, are unclear. In this research, we identified an Arabidopsis mutant, dps1, with greatly reduced sensitivity to Pi starvation. The dps1 phenotypes are caused by a mutation in the previously characterized SVR1 (SUPPRESSION OF VARIAGATION 1) gene, which encodes a chloroplast-localized pseudouridine synthase. The mutation of SVR1 results in defects in chloroplast rRNA biogenesis, which subsequently reduces chloroplast translation. Another mutant, rps5, which contains a mutation in the chloroplast ribosomal protein RPS5 and has reduced chloroplast translation, also displayed decreased sensitivity to Pi starvation. Furthermore, wild type plants treated with lincomycin, a chemical inhibitor of chloroplast translation, showed similar growth phenotypes and Pi starvation responses as dps1 and rps5. These results suggest that impaired chloroplast translation desensitizes plants to Pi starvation. Combined with previously published results showing that enhanced leaf photosynthesis augments plant responses to Pi starvation, we propose that the decrease in responses to Pi starvation in dps1, rps5, and lincomycin-treated plants is due to their reduced demand for Pi input from the environment.

Highlights

Phosphorus (P) is one of essential macronutrients for plant growth and development
The activity of PHR1 is further regulated by SPX1, which forms complex with PHR1 to block its binding to the promoters of many Pi starvationinduced (PSI) genes (Puga et al, 2014). miR399, PHO2, and two other non-coding RNAs, IPS1 and At4, form another signaling pathway that regulates Pi homeostasis in plants (Liu et al, 2014)
To identify novel key factors that determine plant sensitivity to Pi starvation, we screened an Arabidopsis T-DNA insertion library for mutants with altered responses to Pi starvation. This library was constructed by transforming a transgenic line carrying an AtPT2::LUC reporter gene (Koiwa et al, 2006)

Summary

Introduction

Phosphorus (P) is one of essential macronutrients for plant growth and development. Inorganic phosphate (Pi), the major form of P that plants assimilate, is highly immobile in most soils due to its conversion to organophosphates by microorganisms or to its chelation with metals. Plants have developed elaborate strategies to cope with Pi starvation, including the remodeling of root system architecture (RSA); the increase of activities of high affinity Pi transporters; the induction and secretion of acid phosphatases (APases), ribonuclease, Chloroplast and Plant Pi Sensitivity and organic acids; and the accumulation of starch and anthocyanins (Vance et al, 2003). These Pi-starvation responses are controlled by an elaborate gene regulatory network through both local and systemic signaling (Chiou and Lin, 2011). The induced IPS1 and At4 begin to pair with miR399 to inhibit its silencing of PHO2 mRNA and to maintain Pi homeostasis in Pi-starved plants (Franco-Zorrilla et al, 2007)

Methods

Results

Conclusion