Functional characterization of the rice SPX‐MFS family reveals a key role of OsSPX‐MFS1 in controlling phosphate homeostasis in leaves

Abstract

Summary Proteins possessing the SPX domain are found in several proteins involved in inorganic phosphate (Pi) transport and signalling in yeast and plants. Although the functions of several SPX‐domain protein subfamilies have recently been uncovered, the role of the SPX‐MFS subfamily is still unclear. Using quantitative RT‐PCR analysis, we studied the regulation of SPX‐MFS gene expression by the central regulator, OsPHR2 and Pi starvation. The function of OsSPX‐MFS1 in Pi homeostasis was analysed using an OsSPX‐MFS1 mutant (mfs1) and osa‐miR827 overexpression line (miR827‐Oe). Finally, heterologous complementation of a yeast mutant impaired in Pi transporter was used to assess the capacity of OsSPX‐MFS1 to transport Pi. Transcript analyses revealed that members of the SPX‐MFS family were mainly expressed in the shoots, with OsSPX‐MFS1 and OsSPX‐MFS3 being suppressed by Pi deficiency, while OsSPX‐MFS2 was induced. Mutation in OsSPX‐MFS1 (mfs1) and overexpression of the upstream miR827 (miR827‐Oe) plants impaired Pi homeostasis in the leaves. In addition, studies in yeast revealed that OsSPX‐MFS1 may be involved in Pi transport. The results suggest that OsSPX‐MFS1 is a key player in maintaining Pi homeostasis in the leaves, potentially acting as a Pi transporter.

Spatio-Temporal Transcript Profiling of Rice Roots and Shoots in Response to Phosphate Starvation and Recovery

“…This transcript was one of the most highly induced genes in the roots with more than 1400-fold induction, as well as showing a 30-fold increase in the shoot. This locus also overlapped with the genomic location of O. sativa (osa)-miR827a, one of the key miRNAs involved in Pi homeostasis, which acts through the regulation of two target genes, SPX-MFS1 and SPX-MFS2 (Lin et al, 2010;Wang et al, 2012). This locus was considered to be the precursor of osa-miR827, but no cDNA or ESTs were reported for this locus so far (Lacombe et al, 2008), probably due to the fact that this gene is only expressed under Pi-deficient conditions.…”

“…Differential expression analysis revealed that osa-miR827 and osamiR399 were the most induced families in both root and shoot, with miR827 being the most induced miRNA after 21 d of Pi starvation, with more than a 140-fold increase seen in roots (Figures 9A and 9B; see Supplemental Data Set 8 online). These two miRNA families have been shown to be induced by Pi starvation in both Arabidopsis and rice Bari et al, 2006;Lin et al, 2010;Jeong et al, 2011;Wang et al, 2012), with Arabidopsis miR399 negatively regulating genes such as PHO2 and the two Pi transporters Pht1;8 Differentially expressed miRNAs in response to 21 d of Pi starvation in the roots (A) and shoots (B) were identified using the miRanalyzer software. Only significantly differentially expressed miRNAs with a fold change greater than 2 are shown (q value < 0.05).…”

“…In addition to mRNA regulation, microRNAs (miRNAs) function as key regulators of nutrient stress signaling (Chiou, 2007), with miR399 and miR827 regulating Pi homeostasis (Fujii et al, 2005;Chiou et al, 2006;Hsieh et al, 2009;Pant et al, 2009;Lin et al, 2010;Kant et al, 2011;Kuo and Chiou, 2011;Wang et al, 2012). Yet, to date, only a single study was performed to assess miRNA regulation in rice under Pi stress, using plants starved for a short period of time (5 d) and focusing only on miR399 and miR827 (Jeong et al, 2011), thus revealing the need for the identification of Piresponsive miRNAs in rice.…”

Eukaryotic Phosphate Homeostasis: The Inositol Pyrophosphate Perspective

“…The subfamily SPX-MFS (Major Facilitator Superfamily) includes transporters that facilitate the translocation of small solutes, including phosphate [23][24][25]. In A. thaliana there are three members (SPX-MSF1-3).…”

The Relationship between the Instructors’ Organizational Justice Perceptions and Their Hopelessness Levels

“…When the studies conducted on hopelessness in educational organizations are analyzed, it can be understood that these studies were done especially on teenagers having education (Alverson, 2014;Hoy and Tarter, 2004;Kula, 2008;Siyahhan, Aricak and Acar, 2012), university students (Asdigian, 1993;Kılıç, Tektaş and Pala, 2014;Stockum, 1999;Lamis, Saito, Osman, Klibert, Malone and Langhinrichsen-Rohling, 2014;Üngüren, 2007), preservice teachers (Ceyhan, 2004;Dinçer, Yılmaz and Keşan, 2015;Öngen, 2012;Şahin, 2009;Şengül, Güner and Altın, 2014) and teachers (Kiziroğlu, 2012;Taner, 2008;Yıldırım, 2015). Of the studies conducted in the field of education, for example, the results of the study by Üngüren (2007) on 496 tourism students having education at high schools and universities put forth a positive significant relationship between hopelessness and anxiety and it was concluded that as the anxiety levels of the students increase, their hopelessness levels increase, too.…”