Functional analysis and cell-specific expression of a phosphate transporter from tomato

Daram, Pierre; Brunner, Silvia; Persson, Bengt L.; Amrhein, Nikolaus; Bucher, Marcel

doi:10.1007/s004250050394

Cited by 207 publications

(254 citation statements)

References 31 publications

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“…An actual effect of Cd 2ϩ on the electric component of ⌬ H ϩ can be excluded because the values of E m in root cells were only slightly more negative in Cd-treated than in control plants (Table II). Similar to sulfate, K ϩ and Pi transports are dependent on H ϩ electrochemical gradient across the plasma membrane (UllrichEberius et al, 1984;Thibaud et al, 1988;Sacchi and Cocucci, 1992;Daram et al, 1998), but unlike sulfate, their uptake was inhibited or unaffected, respectively, by Cd treatment (Fig. 4, B and C).…”

Section: Discussionmentioning

confidence: 82%

Cadmium-Induced Sulfate Uptake in Maize Roots

et al. 2002

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The effect of cadmium (Cd) on high-affinity sulfate transport of maize (Zea mays) roots was studied and related to the changes in the levels of sulfate and nonprotein thiols during Cd-induced phytochelatin (PC) biosynthesis. Ten micromolar CdCl 2 in the nutrient solution induced a 100% increase in sulfate uptake by roots. This was not observed either for potassium or phosphate uptake, suggesting a specific effect of Cd 2ϩ on sulfate transport. The higher sulfate uptake was not dependent on a change in the proton motive force that energizes it. In fact, in Cd-treated plants, the transmembrane electric potential difference of root cortical cells was only slightly more negative than in the controls, the external pH did not change, and the activity of the plasma membrane H ϩ -ATPase did not increase. Kinetics analysis showed that in the range of the high-affinity sulfate transport systems, 10 to 250 m, Cd exposure did not influence the K m value (about 20 m), whereas it doubled the V max value with respect to the control. Northern-blot analysis showed that Cd-induced sulfate uptake was related to a higher level of mRNA encoding for a putative high-affinity sulfate transporter in roots. Cd-induced sulfate uptake was associated to both a decrease in the contents of sulfate and glutathione and synthesis of a large amount of PCs. These results suggest that Cd-induced sulfate uptake depends on a pretranslational regulation of the high-affinity sulfate transporter gene and that this response is necessary for sustaining the higher sulfur demand during PC biosynthesis.

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Section: Discussionmentioning

confidence: 82%

Cadmium-Induced Sulfate Uptake in Maize Roots

et al. 2002

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“…At least nine genes showing similarity to AtPT1 have been identified in Arabidopsis from expressed sequence tags and genome sequence analysis, although the expression of only AtPT1 and AtPT2 are readily detectable by RNA gel blot analysis (Muchhal et al, 1996;Lu et al, 1997;Mitsukawa et al, 1997;Smith et al, 1997;Okumura et al, 1998;Raghothama, 2000). Homologs of AtPT1 also have been identified in Catharanthus roseus ( CrPT1 ; Kai et al, 1997), potato ( StPT1 and StPT2 ; Leggewie et al, 1997), tomato ( LePT1 and LePT2 ; Daram et al, 1998;Liu et al, 1998a), Medicago trunculata ( MtPT1 and MtPT2 ; Liu et al, 1998b), tobacco ( NtPT1 ), and wheat ( TaPT1 ) (Raghothama, 2000). All members of this family of high-affinity phosphate transporters share extensive amino acid homology with each other and show significant homology with the yeast Pho84 H ϩ -Pi cotransporter.…”

Section: Introductionmentioning

confidence: 99%

Identification and Characterization of the Arabidopsis PHO1 Gene Involved in Phosphate Loading to the Xylem

et al. 2002

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The Arabidopsis mutant pho1 is deficient in the transfer of Pi from root epidermal and cortical cells to the xylem. The PHO1 gene was identified by a map-based cloning strategy. The N-terminal half of PHO1 is mainly hydrophilic, whereas the C-terminal half has six potential membrane-spanning domains. PHO1 shows no homology with any characterized solute transporter, including the family of H ؉ -Pi cotransporters identified in plants and fungi. PHO1 shows highest homology with the Rcm1 mammalian receptor for xenotropic murine leukemia retroviruses and with the Saccharomyces cerevisiae Syg1 protein involved in the mating pheromone signal transduction pathway. PHO1 is expressed predominantly in the roots and is upregulated weakly under Pi stress. Studies with PHO1 promoter-␤ -glucuronidase constructs reveal predominant expression of the PHO1 promoter in the stelar cells of the root and the lower part of the hypocotyl. There also is ␤ -glucuronidase staining of endodermal cells that are adjacent to the protoxylem vessels. The Arabidopsis genome contains 10 additional genes showing homology with PHO1 . Thus, PHO1 defines a novel class of proteins involved in ion transport in plants. INTRODUCTIONThe radial movement of ions from root epidermal and cortical cells to the xylem can be mediated by two major pathways. In the apoplastic pathway, ions move radially toward the stele through the extracellular space, whereas in the symplastic pathway, ions move intracellularly from cell to cell via plasmodesmata (Bowling, 1981;Clarkson, 1993). Although a third pathway is possible, namely, one in which ions move from cell to cell through a successive uptake and release of ions from and into the extracellular space, the high energy requirement of this pathway makes it unlikely to play a major role in ion transport to the xylem.The movement of ions and water through the apoplast of the root is blocked at the level of the endoderm by the Casparian strip, a zone in which the cell wall is impregnated with hydrophobic compounds such as suberin and lignin. Thus, passage of ions beyond the Casparian strip and toward the stele must proceed via the symplasm. Once in the cells of the stele, the release of ions into the xylem requires their efflux out of the stelar cells. Thus, radial transport of ions from the external solution to the xylem requires a minimum of two passages across the plasma membrane, once for the uptake of ions into the epidermal, cortical, or outer surface of the endodermal cells, and then again for the efflux of ions out of the stelar cells before entering the xylem vessel (Bowling, 1981;Clarkson, 1993).The uptake of anions such as Pi into a cell is an energyrequiring process. The negatively charged phosphate ion (HPO 4 Ϫ 2 or H 2 PO 4 Ϫ ) must move against an electrical gradient, the interior of the cell being negatively charged ( ‫ف‬ Ϫ 100 mV), as well as against a concentration gradient, the intracellular concentration of Pi being 1000 to 10,000 times higher than the extracellular concentration (the concentration of P...

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“…The higher level of expression of rRNA comparing to the target mRNA has been pointed out as a disadvantage in its use as internal standard. Many other genes including ubiquitin and eIF4AII have also been identified as housekeeping genes in different tissues (Daram et al 1998;Eisenberg and Levanon 2003). To ensure the credibility of the results in a set experimental design using gene controls, a previous study should be performed to determine the most suitable housekeeping genes (Giulietti et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of control transcripts in real-time RT-PCR expression analysis during maritime pine embryogenesis

Gonçalves

Cairney

Marôco

et al. 2005

Planta

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In order to determine the suitability of reference or housekeeping genes as internal controls in real-time reverse transcriptase PCR (RT-PCR) assays for quantification of target mRNAs, we studied the levels of expression of four candidate reference genes in maritime pine by real-time RT-PCR. The expression levels obtained for glyceraldehyde-3-phosphate-dehydrogenase, 18S ribosomal RNA, eukaryotic translation initiation factor eIF4AII and ubiquitin in nine stages of embryo development revealed that none of the genes tested proved to be suitable as an internal control. Copy number quantification of the four transcripts showed an average relative variation of seven fold. We propose that the combination of a precise method for RNA quantification, internal controls for monitoring RT reaction and PCR efficiency and a robust external standard curve can guarantee a reliable absolute quantification of mRNA transcripts in real time RT-PCR. This approach may avoid the controversy in the use of housekeeping genes and may assume special significance in tissues undergoing developmental changes.

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Functional analysis and cell-specific expression of a phosphate transporter from tomato

Cited by 207 publications

References 31 publications

Cadmium-Induced Sulfate Uptake in Maize Roots

Cadmium-Induced Sulfate Uptake in Maize Roots

Identification and Characterization of the Arabidopsis PHO1 Gene Involved in Phosphate Loading to the Xylem

Evaluation of control transcripts in real-time RT-PCR expression analysis during maritime pine embryogenesis

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