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Coordination between zinc and phosphate homeostasis involves the transcription factor PHR1, the phosphate exporter PHO1, and its homologue PHO1;H3 in Arabidopsis.

Khan GA, Bouraine S, Wege S, Li Y, de Carbonnel M, Berthomieu P, Poirier Y, Rouached H - J. Exp. Bot. (2014)

Bottom Line: This work aimed at examining the effects of Zn deficiency on Pi accumulation in Arabidopsis thaliana and uncovering genes involved in the Zn-Pi synergy.Zn deprivation had a very limited effect on transcript levels of Pi-starvation-responsive genes such as AT4, IPS1, and microRNA399, or on of members of the high-affinity Pi transporter family PHT1.This was, however, not observed in a pho1 pho1;h3 double mutant, suggesting that PHO1;H3 restricts root-to-shoot Pi transfer requiring PHO1 function for Pi homeostasis in response to Zn deficiency.

View Article: PubMed Central - PubMed

Affiliation: Département de Biologie Moléculaire Végétale, Biophore, Université de Lausanne, CH-1015 Lausanne, Switzerland.

ABSTRACT
Interactions between zinc (Zn) and phosphate (Pi) nutrition in plants have long been recognized, but little information is available on their molecular bases and biological significance. This work aimed at examining the effects of Zn deficiency on Pi accumulation in Arabidopsis thaliana and uncovering genes involved in the Zn-Pi synergy. Wild-type plants as well as mutants affected in Pi signalling and transport genes, namely the transcription factor PHR1, the E2-conjugase PHO2, and the Pi exporter PHO1, were examined. Zn deficiency caused an increase in shoot Pi content in the wild type as well as in the pho2 mutant, but not in the phr1 or pho1 mutants. This indicated that PHR1 and PHO1 participate in the coregulation of Zn and Pi homeostasis. Zn deprivation had a very limited effect on transcript levels of Pi-starvation-responsive genes such as AT4, IPS1, and microRNA399, or on of members of the high-affinity Pi transporter family PHT1. Interestingly, one of the PHO1 homologues, PHO1;H3, was upregulated in response to Zn deficiency. The expression pattern of PHO1 and PHO1;H3 were similar, both being expressed in cells of the root vascular cylinder and both localized to the Golgi when expressed transiently in tobacco cells. When grown in Zn-free medium, pho1;h3 mutant plants displayed higher Pi contents in the shoots than wild-type plants. This was, however, not observed in a pho1 pho1;h3 double mutant, suggesting that PHO1;H3 restricts root-to-shoot Pi transfer requiring PHO1 function for Pi homeostasis in response to Zn deficiency.

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mRNA accumulation of members of the PHO1 gene family in response to the availability of Pi and Zn in shoots (A) and roots (B). Wild-type plants were grown in a vertical position on agar-solidified media containing 1mM Pi and 15 μM Zn (+Pi,+Zn), 15 μM Zn and no Pi (–Pi,+Zn), or 1mM Pi and no Zn (+Pi,–Zn). Shoots and roots of 20-d-old plants were separately harvested and mRNA accumulation was quantified by quantitative reverse-transcription PCR. mRNA abundance was normalized to the mRNA abundance of the UBQ10 control gene and expressed as relative values against wild-type plants grown in +Pi,+Zn medium. Individual measurements were obtained from the analysis of shoots or roots collected from a pool of at least 10 plants. Error bars correspond to standard deviation from three biological replicates. Asterisks indicate statistically significant differences compared to the +Pi +Zn treatment for each gene (P <0.05).
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Figure 4: mRNA accumulation of members of the PHO1 gene family in response to the availability of Pi and Zn in shoots (A) and roots (B). Wild-type plants were grown in a vertical position on agar-solidified media containing 1mM Pi and 15 μM Zn (+Pi,+Zn), 15 μM Zn and no Pi (–Pi,+Zn), or 1mM Pi and no Zn (+Pi,–Zn). Shoots and roots of 20-d-old plants were separately harvested and mRNA accumulation was quantified by quantitative reverse-transcription PCR. mRNA abundance was normalized to the mRNA abundance of the UBQ10 control gene and expressed as relative values against wild-type plants grown in +Pi,+Zn medium. Individual measurements were obtained from the analysis of shoots or roots collected from a pool of at least 10 plants. Error bars correspond to standard deviation from three biological replicates. Asterisks indicate statistically significant differences compared to the +Pi +Zn treatment for each gene (P <0.05).

Mentions: Expression of the PHO1 homologue PHO1;H3 is regulated by Zn deficiency. The effect of Zn deprivation on the expression of PHO1 and its 10 homologues was explored. Transcript accumulation was analysed by qPCR in shoots and roots of wild-type plants grown in media with low and high Zn or Pi (Fig. 4). In line with previous results, PHO1 and its closest homologue PHO1;H1 were induced in roots and in roots and shoots, respectively, in response to Pi starvation (Stefanovic et al, 2007; Ribot et al., 2008a). The transcript abundances of all other PHO1 homologues were not significantly altered. In response to Zn deprivation, transcript accumulation only of PHO1;H3 was changed, showing upregulation in both roots and shoots. Interestingly, the expression of PHO1;H3 was not upregulated by Pi starvation. This results suggests that PHO1;H3 plays a specific role in the regulation of Pi homeostasis under Zn deficiency.


Coordination between zinc and phosphate homeostasis involves the transcription factor PHR1, the phosphate exporter PHO1, and its homologue PHO1;H3 in Arabidopsis.

Khan GA, Bouraine S, Wege S, Li Y, de Carbonnel M, Berthomieu P, Poirier Y, Rouached H - J. Exp. Bot. (2014)

mRNA accumulation of members of the PHO1 gene family in response to the availability of Pi and Zn in shoots (A) and roots (B). Wild-type plants were grown in a vertical position on agar-solidified media containing 1mM Pi and 15 μM Zn (+Pi,+Zn), 15 μM Zn and no Pi (–Pi,+Zn), or 1mM Pi and no Zn (+Pi,–Zn). Shoots and roots of 20-d-old plants were separately harvested and mRNA accumulation was quantified by quantitative reverse-transcription PCR. mRNA abundance was normalized to the mRNA abundance of the UBQ10 control gene and expressed as relative values against wild-type plants grown in +Pi,+Zn medium. Individual measurements were obtained from the analysis of shoots or roots collected from a pool of at least 10 plants. Error bars correspond to standard deviation from three biological replicates. Asterisks indicate statistically significant differences compared to the +Pi +Zn treatment for each gene (P <0.05).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3924728&req=5

Figure 4: mRNA accumulation of members of the PHO1 gene family in response to the availability of Pi and Zn in shoots (A) and roots (B). Wild-type plants were grown in a vertical position on agar-solidified media containing 1mM Pi and 15 μM Zn (+Pi,+Zn), 15 μM Zn and no Pi (–Pi,+Zn), or 1mM Pi and no Zn (+Pi,–Zn). Shoots and roots of 20-d-old plants were separately harvested and mRNA accumulation was quantified by quantitative reverse-transcription PCR. mRNA abundance was normalized to the mRNA abundance of the UBQ10 control gene and expressed as relative values against wild-type plants grown in +Pi,+Zn medium. Individual measurements were obtained from the analysis of shoots or roots collected from a pool of at least 10 plants. Error bars correspond to standard deviation from three biological replicates. Asterisks indicate statistically significant differences compared to the +Pi +Zn treatment for each gene (P <0.05).
Mentions: Expression of the PHO1 homologue PHO1;H3 is regulated by Zn deficiency. The effect of Zn deprivation on the expression of PHO1 and its 10 homologues was explored. Transcript accumulation was analysed by qPCR in shoots and roots of wild-type plants grown in media with low and high Zn or Pi (Fig. 4). In line with previous results, PHO1 and its closest homologue PHO1;H1 were induced in roots and in roots and shoots, respectively, in response to Pi starvation (Stefanovic et al, 2007; Ribot et al., 2008a). The transcript abundances of all other PHO1 homologues were not significantly altered. In response to Zn deprivation, transcript accumulation only of PHO1;H3 was changed, showing upregulation in both roots and shoots. Interestingly, the expression of PHO1;H3 was not upregulated by Pi starvation. This results suggests that PHO1;H3 plays a specific role in the regulation of Pi homeostasis under Zn deficiency.

Bottom Line: This work aimed at examining the effects of Zn deficiency on Pi accumulation in Arabidopsis thaliana and uncovering genes involved in the Zn-Pi synergy.Zn deprivation had a very limited effect on transcript levels of Pi-starvation-responsive genes such as AT4, IPS1, and microRNA399, or on of members of the high-affinity Pi transporter family PHT1.This was, however, not observed in a pho1 pho1;h3 double mutant, suggesting that PHO1;H3 restricts root-to-shoot Pi transfer requiring PHO1 function for Pi homeostasis in response to Zn deficiency.

View Article: PubMed Central - PubMed

Affiliation: Département de Biologie Moléculaire Végétale, Biophore, Université de Lausanne, CH-1015 Lausanne, Switzerland.

ABSTRACT
Interactions between zinc (Zn) and phosphate (Pi) nutrition in plants have long been recognized, but little information is available on their molecular bases and biological significance. This work aimed at examining the effects of Zn deficiency on Pi accumulation in Arabidopsis thaliana and uncovering genes involved in the Zn-Pi synergy. Wild-type plants as well as mutants affected in Pi signalling and transport genes, namely the transcription factor PHR1, the E2-conjugase PHO2, and the Pi exporter PHO1, were examined. Zn deficiency caused an increase in shoot Pi content in the wild type as well as in the pho2 mutant, but not in the phr1 or pho1 mutants. This indicated that PHR1 and PHO1 participate in the coregulation of Zn and Pi homeostasis. Zn deprivation had a very limited effect on transcript levels of Pi-starvation-responsive genes such as AT4, IPS1, and microRNA399, or on of members of the high-affinity Pi transporter family PHT1. Interestingly, one of the PHO1 homologues, PHO1;H3, was upregulated in response to Zn deficiency. The expression pattern of PHO1 and PHO1;H3 were similar, both being expressed in cells of the root vascular cylinder and both localized to the Golgi when expressed transiently in tobacco cells. When grown in Zn-free medium, pho1;h3 mutant plants displayed higher Pi contents in the shoots than wild-type plants. This was, however, not observed in a pho1 pho1;h3 double mutant, suggesting that PHO1;H3 restricts root-to-shoot Pi transfer requiring PHO1 function for Pi homeostasis in response to Zn deficiency.

Show MeSH