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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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Effect of Zn availability on Pi contents in roots and shoots of Arabidopsis. Wild-type and phr1, pho1-2 and pho2-1 mutant plants were grown vertically 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). Pi concentrations were quantified in shoots (A) and roots (B) of 20-d-old plants. Individual measurements were obtained from the analysis of shoots or roots collected from a pool of at least seven plants. Error bars correspond to standard deviation from three biological replicates. Asterisks indicate statistically significant differences compared to the +Pi,+Zn treatment within each genotype (P < 0.05).
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Figure 1: Effect of Zn availability on Pi contents in roots and shoots of Arabidopsis. Wild-type and phr1, pho1-2 and pho2-1 mutant plants were grown vertically 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). Pi concentrations were quantified in shoots (A) and roots (B) of 20-d-old plants. Individual measurements were obtained from the analysis of shoots or roots collected from a pool of at least seven plants. Error bars correspond to standard deviation from three biological replicates. Asterisks indicate statistically significant differences compared to the +Pi,+Zn treatment within each genotype (P < 0.05).

Mentions: Zn deficiency increases the Pi content in the shoots of Arabidopsis wild-type plants and pho2 mutant plants but not in phr1 and pho1 mutant plants. In order to determine the effect of Zn deficiency on Pi distribution in Arabidopsis tissues, plants were grown in media with either low Zn (0 μM Zn) or low Pi (10 μM Pi) and compared to those grown on complete medium (1mM Pi and 15 μM Zn). Mutants affected in interorgan Pi distribution or Pi signalling were included in this experiment, namely pho1, pho2, and phr1. The pho1 and pho2 mutants are characterized by accumulation of low Pi and high Pi in shoots, respectively (Poirier et al., 1991; Delhaize and Randall, 1995). The phr1 mutant is affected in the responses to Pi deficiency, including alteration of the expression of several Pi-starvation-induced genes (Rubio et al., 2001). Shoots and roots of 20-d-old plants were collected separately and Pi contents were determined (Fig. 1). As expected, Pi starvation led to a decrease in Pi content in shoots and roots. Interestingly the Pi concentration increased by 25% in shoots of wild-type and pho2 plants grown in Zn-deficient medium compared to Zn-sufficient medium. No change in Pi concentration was however observed in the shoots of phr1 and pho1 mutants grown on Zn-sufficient or Zn-deficient media (Fig. 1). In roots, Zn deprivation had no impact on Pi accumulation, except for the pho1 mutant in which a 15% increase in Pi concentration (P < 0.05) was observed. Overall, these results imply the existence of a process leading to the accumulation of Pi in the shoots of plants under Zn deprivation. PHO1 and PHR1 participate in this process.


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)

Effect of Zn availability on Pi contents in roots and shoots of Arabidopsis. Wild-type and phr1, pho1-2 and pho2-1 mutant plants were grown vertically 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). Pi concentrations were quantified in shoots (A) and roots (B) of 20-d-old plants. Individual measurements were obtained from the analysis of shoots or roots collected from a pool of at least seven plants. Error bars correspond to standard deviation from three biological replicates. Asterisks indicate statistically significant differences compared to the +Pi,+Zn treatment within each genotype (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 1: Effect of Zn availability on Pi contents in roots and shoots of Arabidopsis. Wild-type and phr1, pho1-2 and pho2-1 mutant plants were grown vertically 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). Pi concentrations were quantified in shoots (A) and roots (B) of 20-d-old plants. Individual measurements were obtained from the analysis of shoots or roots collected from a pool of at least seven plants. Error bars correspond to standard deviation from three biological replicates. Asterisks indicate statistically significant differences compared to the +Pi,+Zn treatment within each genotype (P < 0.05).
Mentions: Zn deficiency increases the Pi content in the shoots of Arabidopsis wild-type plants and pho2 mutant plants but not in phr1 and pho1 mutant plants. In order to determine the effect of Zn deficiency on Pi distribution in Arabidopsis tissues, plants were grown in media with either low Zn (0 μM Zn) or low Pi (10 μM Pi) and compared to those grown on complete medium (1mM Pi and 15 μM Zn). Mutants affected in interorgan Pi distribution or Pi signalling were included in this experiment, namely pho1, pho2, and phr1. The pho1 and pho2 mutants are characterized by accumulation of low Pi and high Pi in shoots, respectively (Poirier et al., 1991; Delhaize and Randall, 1995). The phr1 mutant is affected in the responses to Pi deficiency, including alteration of the expression of several Pi-starvation-induced genes (Rubio et al., 2001). Shoots and roots of 20-d-old plants were collected separately and Pi contents were determined (Fig. 1). As expected, Pi starvation led to a decrease in Pi content in shoots and roots. Interestingly the Pi concentration increased by 25% in shoots of wild-type and pho2 plants grown in Zn-deficient medium compared to Zn-sufficient medium. No change in Pi concentration was however observed in the shoots of phr1 and pho1 mutants grown on Zn-sufficient or Zn-deficient media (Fig. 1). In roots, Zn deprivation had no impact on Pi accumulation, except for the pho1 mutant in which a 15% increase in Pi concentration (P < 0.05) was observed. Overall, these results imply the existence of a process leading to the accumulation of Pi in the shoots of plants under Zn deprivation. PHO1 and PHR1 participate in this process.

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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