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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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Comparison of the six Arabidopsis PMT proteins. Schematic alignment of the deduced protein sequences (black bars) of AtPMT1 to AtPMT6 based on the intron positions (arrows) in the respective genes. Grey vertical bars (I–XII) indicate the positions of the predicted transmembrane helices, thin lines show two small gaps in the AtPMT4 sequence. Numbers of amino acids encoded by the different exons are indicated (white).
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fig1: Comparison of the six Arabidopsis PMT proteins. Schematic alignment of the deduced protein sequences (black bars) of AtPMT1 to AtPMT6 based on the intron positions (arrows) in the respective genes. Grey vertical bars (I–XII) indicate the positions of the predicted transmembrane helices, thin lines show two small gaps in the AtPMT4 sequence. Numbers of amino acids encoded by the different exons are indicated (white).

Mentions: In silico analyses of the Arabidopsis genome revealed five open reading frames (ORFs) for transporters with significant homology to the previously characterized Arabidopsis plasma membrane polyol transporter AtPMT5 (At3g18830; Klepek et al., 2005). Two of these genes, AtPMT1 (At2g16120) and AtPMT2 (At2g16130), are located on chromosome 2 with their start ATGs being separated by 6881 nucleotides. Both genes are interrupted by 2 introns, and in both genes these introns are inserted at identical positions (after nucleotides 127 and 474 of the open reading frame) yielding exons that encode identical numbers of amino acids (Fig. 1). The first of these two introns is conserved in all AtPMT genes, the second only in AtPMT1, AtPMT2, and AtPMT5. The high degree of similarity in the coding regions of AtPMT1 and AtPMT2 (93.6% identity on the amino acid level) is conserved also within their intron sequences that are 83.3% (1st intron; 91 bp in AtPMT1 and 94 bp in AtPMT2) and 68.7% identical (2nd intron; 88 bp in AtPMT1 and 92 bp in AtPMT2). Moreover, the first 500 nucleotides of the 5′-flanking sequences share 76.60% identity. Together, these data suggest that AtPMT1 and AtPMT2 are the result of a gene duplication in the recent history of Arabidopsis evolution. As a result of this high degree of sequence similarity, microarrays do not discriminate between AtPMT1 and AtPMT2 expression. They do show, however, that AtPMT1 and AtPMT2 are the PMT genes with the lowest expression levels in Arabidopsis (https://www.genevestigator.com/).


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)

Comparison of the six Arabidopsis PMT proteins. Schematic alignment of the deduced protein sequences (black bars) of AtPMT1 to AtPMT6 based on the intron positions (arrows) in the respective genes. Grey vertical bars (I–XII) indicate the positions of the predicted transmembrane helices, thin lines show two small gaps in the AtPMT4 sequence. Numbers of amino acids encoded by the different exons are indicated (white).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig1: Comparison of the six Arabidopsis PMT proteins. Schematic alignment of the deduced protein sequences (black bars) of AtPMT1 to AtPMT6 based on the intron positions (arrows) in the respective genes. Grey vertical bars (I–XII) indicate the positions of the predicted transmembrane helices, thin lines show two small gaps in the AtPMT4 sequence. Numbers of amino acids encoded by the different exons are indicated (white).
Mentions: In silico analyses of the Arabidopsis genome revealed five open reading frames (ORFs) for transporters with significant homology to the previously characterized Arabidopsis plasma membrane polyol transporter AtPMT5 (At3g18830; Klepek et al., 2005). Two of these genes, AtPMT1 (At2g16120) and AtPMT2 (At2g16130), are located on chromosome 2 with their start ATGs being separated by 6881 nucleotides. Both genes are interrupted by 2 introns, and in both genes these introns are inserted at identical positions (after nucleotides 127 and 474 of the open reading frame) yielding exons that encode identical numbers of amino acids (Fig. 1). The first of these two introns is conserved in all AtPMT genes, the second only in AtPMT1, AtPMT2, and AtPMT5. The high degree of similarity in the coding regions of AtPMT1 and AtPMT2 (93.6% identity on the amino acid level) is conserved also within their intron sequences that are 83.3% (1st intron; 91 bp in AtPMT1 and 94 bp in AtPMT2) and 68.7% identical (2nd intron; 88 bp in AtPMT1 and 92 bp in AtPMT2). Moreover, the first 500 nucleotides of the 5′-flanking sequences share 76.60% identity. Together, these data suggest that AtPMT1 and AtPMT2 are the result of a gene duplication in the recent history of Arabidopsis evolution. As a result of this high degree of sequence similarity, microarrays do not discriminate between AtPMT1 and AtPMT2 expression. They do show, however, that AtPMT1 and AtPMT2 are the PMT genes with the lowest expression levels in Arabidopsis (https://www.genevestigator.com/).

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