These authors contributed equally to this work.
Involvement of OsSPX1 in phosphate homeostasis in rice
Article first published online: 22 DEC 2008
© 2008 The Authors. Journal compilation © 2008 Blackwell Publishing Ltd
The Plant Journal
Volume 57, Issue 5, pages 895–904, March 2009
How to Cite
Wang, C., Ying, S., Huang, H., Li, K., Wu, P. and Shou, H. (2009), Involvement of OsSPX1 in phosphate homeostasis in rice. The Plant Journal, 57: 895–904. doi: 10.1111/j.1365-313X.2008.03734.x
- Issue published online: 19 FEB 2009
- Article first published online: 22 DEC 2008
- Received 3 September 2008; revised 19 October 2008; accepted 23 October 2008; published online 22 December 2008.
- SPX domain;
Arabidopsis 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.