Involvement of OsSPX1 in phosphate homeostasis in rice

Abstract

These authors contributed equally to this work. SummaryArabidopsis thaliana SPX (SYG/PHO81/XPR1) domain genes have recently been shown to be involved in the phosphate (Pi) signaling pathway. We show here that a rice (Oryza sativa) SPX gene, OsSPX1, is specifically induced by Pi starvation in roots. Suppression of OsSPX1 by RNA interference resulted in severe signs of toxicity caused by the over-accumulation of Pi, similar to that found in OsPHR2 (phosphate starvation response transcription factor 2) overexpressors and pho2 (phosphate-responsive mutant 2). Quantitative RT-PCR showed that expression of OsSPX1 was strongly induced in OsPHR2 overexpression and pho2 mutant plants, indicating that OsSPX1 occurs downstream of OsPHR2 and PHO2. The expression of 10 genes associated with the phosphate-starvation signal pathways was analyzed. Expression of OsPT2 (phosphate transporter 2) and OsPT8 was significantly induced in OsSPX1-RNAi (OsSPX1-Ri) plants, suggesting that over-accumulation of Pi in OsSPX1-Ri plants results from an increase in Pi transport. In contrast, overexpression of OsSPX1 suppressed the induction of expression by Pi starvation of all 10 phosphate starvation-induced genes tested: IPS1 (induced by phosphate starvation 1), IPS2, OsPAP10 (purple acid phosphatase 10), OsSQD2 (sulfoquinovosyldiacylglycerol 2), miR399d and miR399j (microRNA 399), OsPT2, OsPT3, OsPT6 and OsPT8. This suggests that OsSPX1 acts via a negative feedback loop to optimize growth under phosphate-limited conditions.

Phosphate Utilization Efficiency Correlates with Expression of Low-Affinity Phosphate Transporters and Noncoding RNA, IPS1, in Barley

“…in Pi retranslocation and regulated by the miR399-PHO2 signaling pathway (Wang et al, 2009;Liu et al, 2010). In addition, the expression of HvPHT1;3 in roots mimics that of HvPHT1;6 (Fig.…”

mRNA-Seq Reveals a Comprehensive Transcriptome Profile of Rice under Phosphate Stress

“…Several SPX (SYG/PHO81/XPR1) domain-containing genes involved in response to environmental cues or internal regulation of nutrition homeostasis such as SPX1, SPX2, and SPX6 were upregulated only in shoot during late -P stress. In rice, SPX1 is partly involved in regulating the induction of some Pi transporters (Wang et al 2009b). Histone H4 (Os04t0583600) and histone H2B (Os05t0574300) were upregulated in shoot during early -P stress whereas histone H1 (Os03t0799000) and histone H2B (Os01t0152900) were downregulated in shoot during late -P stress thereby supporting the chromatin-level regulation of response to Pi starvation (Smith et al 2010).…”

The Phosphate Fast-Responsive Genes PECP1 and PPsPase1 Affect Phosphocholine and Phosphoethanolamine Content

“…Furthermore, their corresponding mutants exhibit altered gene induction and classical Pi starvation responses, including diminished effects on Pi content and lipid remobilization (Pant et al, 2015). Candidates for the systemic control of Pi starvation responses have been proposed, including substantial transport of mRNAs throughout the plant (as reviewed in Puga et al, 2017), and the direct sensing of Pi concentration (or Pi-containing metabolites) by SPX-type proteins (Wang et al, 2009;Puga et al, 2014;Wild et al, 2016).…”

“…Furthermore, their corresponding mutants exhibit altered gene induction and classical Pi starvation responses, including diminished effects on Pi content and lipid remobilization (Pant et al, 2015). Candidates for the systemic control of Pi starvation responses have been proposed, including substantial transport of mRNAs throughout the plant (as reviewed in Puga et al, 2017), and the direct sensing of Pi concentration (or Pi-containing metabolites) by SPX-type proteins (Wang et al, 2009;Puga et al, 2014;Wild et al, 2016).Two phosphatases belonging to the haloacid dehalogenase (HAD) superfamily were identified as some of the most strongly induced transcripts following Pi starvation (Bari et al, 2006;Müller et al, 2007;Thibaud et al, 2010). These enzymes were named PPsPase1 (for pyrophosphatase [PPi]-specific phosphatase1) and PECP1 (for phosphoethanolamine (PEth)/ phosphocholine [PCho] phosphatase1) on the basis of their in vitro activity, following their heterologous expression in bacteria and subsequent purification (May et al, 2011(May et al, , 2012.…”