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Arabidopsis thaliana POLYOL/MONOSACCHARIDE TRANSPORTERS 1 and 2: fructose and xylitol/H+ symporters in pollen and young xylem cells.

Klepek YS, Volke M, Konrad KR, Wippel K, Hoth S, Hedrich R, Sauer N - J. Exp. Bot. (2009)

Bottom Line: Analyses of reporter genes performed with AtPMT1 or AtPMT2 promoter sequences showed expression in mature (AtPMT2) or germinating (AtPMT1) pollen grains, as well as in growing pollen tubes, hydathodes, and young xylem cells (both genes).The expression was confirmed with an anti-AtPMT1/AtPMT2 antiserum (alphaAtPMT1/2) raised against peptides conserved in AtPMT1 and AtPMT2.The physiological roles of the proteins are discussed and related to plant cell wall modifications.

View Article: PubMed Central - PubMed

Affiliation: Molekulare Pflanzenphysiologie, Universität Erlangen-Nürnberg, Staudtstrasse 5, Erlangen, Germany.

ABSTRACT
The genome of Arabidopsis thaliana contains six genes, AtPMT1 to AtPMT6 (Arabidopsis thaliana POLYOL/MONOSACCHARIDE TRANSPORTER 1-6), which form a distinct subfamily within the large family of more than 50 monosaccharide transporter-like (MST-like) genes. So far, only AtPMT5 [formerly named AtPLT5 (At3g18830)] has been characterized and was shown to be a plasma membrane-localized H(+)-symporter with broad substrate specificity. The characterization of AtPMT1 (At2g16120) and AtPMT2 (At2g16130), two other, almost identical, members of this transporter subfamily, are presented here. Expression of the AtPMT1 and AtPMT2 cDNAs in baker's yeast (Saccharomyces cerevisiae) revealed that these proteins catalyse the energy-dependent, high-capacity transport of fructose and xylitol, and the transport of several other compounds with lower rates. Expression of their cRNAs in Xenopus laevis oocytes showed that both proteins are voltage-dependent and catalyse the symport of their substrates with protons. Fusions of AtPMT1 or AtPMT2 with the green fluorescent protein (GFP) localized to Arabidopsis plasma membranes. Analyses of reporter genes performed with AtPMT1 or AtPMT2 promoter sequences showed expression in mature (AtPMT2) or germinating (AtPMT1) pollen grains, as well as in growing pollen tubes, hydathodes, and young xylem cells (both genes). The expression was confirmed with an anti-AtPMT1/AtPMT2 antiserum (alphaAtPMT1/2) raised against peptides conserved in AtPMT1 and AtPMT2. The physiological roles of the proteins are discussed and related to plant cell wall modifications.

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Determination of the Km-values for xylitol for AtPMT1 and AtPMT2. Michaelis–Menten-type kinetics for xylitol uptake were determined (A) in AtPMT1-expressing (strain VMY15) and (B) AtPMT2-expressing (strain YKY6) yeast cells. Inserts show Lineweaver–Burke plots of the same data sets (±SD; n=3).
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fig3: Determination of the Km-values for xylitol for AtPMT1 and AtPMT2. Michaelis–Menten-type kinetics for xylitol uptake were determined (A) in AtPMT1-expressing (strain VMY15) and (B) AtPMT2-expressing (strain YKY6) yeast cells. Inserts show Lineweaver–Burke plots of the same data sets (±SD; n=3).

Mentions: When determining the Km-values of AtPMT1 and AtPMT2 for their putatively best substrate xylitol, almost identical affinities were obtained, with 0.14±0.02 for AtPMT1 and 0.18±0.01 for AtPMT2 (Fig. 3). In addition, the Km of AtPMT1 was determined for sorbitol [0.77±0.12 mM (graph not shown)] and the Km of AtPMT2 was determined for glucose [1.25±0.4 mM (graph not shown)]. These results confirm that xylitol is the best substrate of both transporters.


Arabidopsis thaliana POLYOL/MONOSACCHARIDE TRANSPORTERS 1 and 2: fructose and xylitol/H+ symporters in pollen and young xylem cells.

Klepek YS, Volke M, Konrad KR, Wippel K, Hoth S, Hedrich R, Sauer N - J. Exp. Bot. (2009)

Determination of the Km-values for xylitol for AtPMT1 and AtPMT2. Michaelis–Menten-type kinetics for xylitol uptake were determined (A) in AtPMT1-expressing (strain VMY15) and (B) AtPMT2-expressing (strain YKY6) yeast cells. Inserts show Lineweaver–Burke plots of the same data sets (±SD; n=3).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2803217&req=5

fig3: Determination of the Km-values for xylitol for AtPMT1 and AtPMT2. Michaelis–Menten-type kinetics for xylitol uptake were determined (A) in AtPMT1-expressing (strain VMY15) and (B) AtPMT2-expressing (strain YKY6) yeast cells. Inserts show Lineweaver–Burke plots of the same data sets (±SD; n=3).
Mentions: When determining the Km-values of AtPMT1 and AtPMT2 for their putatively best substrate xylitol, almost identical affinities were obtained, with 0.14±0.02 for AtPMT1 and 0.18±0.01 for AtPMT2 (Fig. 3). In addition, the Km of AtPMT1 was determined for sorbitol [0.77±0.12 mM (graph not shown)] and the Km of AtPMT2 was determined for glucose [1.25±0.4 mM (graph not shown)]. These results confirm that xylitol is the best substrate of both transporters.

Bottom Line: Analyses of reporter genes performed with AtPMT1 or AtPMT2 promoter sequences showed expression in mature (AtPMT2) or germinating (AtPMT1) pollen grains, as well as in growing pollen tubes, hydathodes, and young xylem cells (both genes).The expression was confirmed with an anti-AtPMT1/AtPMT2 antiserum (alphaAtPMT1/2) raised against peptides conserved in AtPMT1 and AtPMT2.The physiological roles of the proteins are discussed and related to plant cell wall modifications.

View Article: PubMed Central - PubMed

Affiliation: Molekulare Pflanzenphysiologie, Universität Erlangen-Nürnberg, Staudtstrasse 5, Erlangen, Germany.

ABSTRACT
The genome of Arabidopsis thaliana contains six genes, AtPMT1 to AtPMT6 (Arabidopsis thaliana POLYOL/MONOSACCHARIDE TRANSPORTER 1-6), which form a distinct subfamily within the large family of more than 50 monosaccharide transporter-like (MST-like) genes. So far, only AtPMT5 [formerly named AtPLT5 (At3g18830)] has been characterized and was shown to be a plasma membrane-localized H(+)-symporter with broad substrate specificity. The characterization of AtPMT1 (At2g16120) and AtPMT2 (At2g16130), two other, almost identical, members of this transporter subfamily, are presented here. Expression of the AtPMT1 and AtPMT2 cDNAs in baker's yeast (Saccharomyces cerevisiae) revealed that these proteins catalyse the energy-dependent, high-capacity transport of fructose and xylitol, and the transport of several other compounds with lower rates. Expression of their cRNAs in Xenopus laevis oocytes showed that both proteins are voltage-dependent and catalyse the symport of their substrates with protons. Fusions of AtPMT1 or AtPMT2 with the green fluorescent protein (GFP) localized to Arabidopsis plasma membranes. Analyses of reporter genes performed with AtPMT1 or AtPMT2 promoter sequences showed expression in mature (AtPMT2) or germinating (AtPMT1) pollen grains, as well as in growing pollen tubes, hydathodes, and young xylem cells (both genes). The expression was confirmed with an anti-AtPMT1/AtPMT2 antiserum (alphaAtPMT1/2) raised against peptides conserved in AtPMT1 and AtPMT2. The physiological roles of the proteins are discussed and related to plant cell wall modifications.

Show MeSH
Related in: MedlinePlus