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Characterization, localization, and seasonal changes of the sucrose transporter FeSUT1 in the phloem of Fraxinus excelsior.

Öner-Sieben S, Rappl C, Sauer N, Stadler R, Lohaus G - J. Exp. Bot. (2015)

Bottom Line: The localization and expression pattern point towards functions of FeSUT1 in phloem loading of sucrose as well as in sucrose retrieval.The elevated expression level of FeSUT1 indicated an increased apoplastic carbon export activity from the leaves during spring and late autumn.It is hypothesized that the importance of apoplastic loading is high under low-sucrose conditions and that the availability of two different phloem-loading mechanisms confers advantages for temperate woody species like F. excelsior.

View Article: PubMed Central - PubMed

Affiliation: Molekulare Pflanzenforschung/Pflanzenbiochemie (Botanik), Bergische Universität Wuppertal, Gaußstraße 20, D-42119 Wuppertal, Germany.

No MeSH data available.


Related in: MedlinePlus

Tissue-specific sugar composition and expression of FeSUT1 in F. excelsior. Samples were taken from three 3-year-old saplings grown in an open greenhouse. (A) Tissue-specific sugar and sugar alcohol content during winter, spring, and summer in F. excelsior. (B) Tissue-specific expression levels of FeSUT1 during winter, spring, and summer. Expression levels of FeSUT1 were normalized to actin and values are given as relative expression levels to the first sample of the measurement (calibrator [cal]). Student’s t-test was performed with P ≤ 0.05 to test for significance of changes compared to calibrator [cal] (asterisk denotes significant difference). Brk, bark; Hex, hexoses; Mal, maltose; RFO, raffinose-oligosaccharide family sugars; Snk lf, sink leaf; Src lf, source leaf; SuAlc, sugar alcohols; Suc, sucrose; Wd, wood.
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Figure 4: Tissue-specific sugar composition and expression of FeSUT1 in F. excelsior. Samples were taken from three 3-year-old saplings grown in an open greenhouse. (A) Tissue-specific sugar and sugar alcohol content during winter, spring, and summer in F. excelsior. (B) Tissue-specific expression levels of FeSUT1 during winter, spring, and summer. Expression levels of FeSUT1 were normalized to actin and values are given as relative expression levels to the first sample of the measurement (calibrator [cal]). Student’s t-test was performed with P ≤ 0.05 to test for significance of changes compared to calibrator [cal] (asterisk denotes significant difference). Brk, bark; Hex, hexoses; Mal, maltose; RFO, raffinose-oligosaccharide family sugars; Snk lf, sink leaf; Src lf, source leaf; SuAlc, sugar alcohols; Suc, sucrose; Wd, wood.

Mentions: After the localization of FeSUT1 in phloem cells, environmental conditions that might influence FeSUT1 expression were analysed. Sugar and sugar alcohol contents as well as mRNA levels of FeSUT1 in different tissues of F. excelsior during different seasons were measured. The overall sugar and sugar alcohol contents were highest in bark [up to 500 µmol g−1 fresh weight (FW)] and wood in winter (Fig. 4A). Because data for sugar content and SUT expression refer to FW, and wood contains less symplast per gram FW than bark or leaves, the values for wood would be even higher if the data referred to the symplast. However, values were given per gram FW to ensure comparability with other published data (e.g. Ferner et al., 2012). In the stem tissues the main sugars were sucrose, hexoses, and RFOs (Fig. 4A). Mannitol was by far the dominant sugar alcohol (more than 90% at the total content of sugar alcohols; data not shown). In spring, sugar and sugar alcohol contents were much lower (below about 80 µmol g−1 FW) in all tissues (bark, wood, sink leaves, and source leaves). Sink leaves and source leaves were defined by size and weight. ‘Source leaves’ in spring were identified as those 80–100% of the size and weight of mature leaves in summer, whereas ‘sink leaves’ had only about 10% of those values. In summer, sugar and sugar alcohol contents in bark and wood were higher than in spring (Fig. 4A) whereas the contents in source leaves were similar or slightly lower.


Characterization, localization, and seasonal changes of the sucrose transporter FeSUT1 in the phloem of Fraxinus excelsior.

Öner-Sieben S, Rappl C, Sauer N, Stadler R, Lohaus G - J. Exp. Bot. (2015)

Tissue-specific sugar composition and expression of FeSUT1 in F. excelsior. Samples were taken from three 3-year-old saplings grown in an open greenhouse. (A) Tissue-specific sugar and sugar alcohol content during winter, spring, and summer in F. excelsior. (B) Tissue-specific expression levels of FeSUT1 during winter, spring, and summer. Expression levels of FeSUT1 were normalized to actin and values are given as relative expression levels to the first sample of the measurement (calibrator [cal]). Student’s t-test was performed with P ≤ 0.05 to test for significance of changes compared to calibrator [cal] (asterisk denotes significant difference). Brk, bark; Hex, hexoses; Mal, maltose; RFO, raffinose-oligosaccharide family sugars; Snk lf, sink leaf; Src lf, source leaf; SuAlc, sugar alcohols; Suc, sucrose; Wd, wood.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4507781&req=5

Figure 4: Tissue-specific sugar composition and expression of FeSUT1 in F. excelsior. Samples were taken from three 3-year-old saplings grown in an open greenhouse. (A) Tissue-specific sugar and sugar alcohol content during winter, spring, and summer in F. excelsior. (B) Tissue-specific expression levels of FeSUT1 during winter, spring, and summer. Expression levels of FeSUT1 were normalized to actin and values are given as relative expression levels to the first sample of the measurement (calibrator [cal]). Student’s t-test was performed with P ≤ 0.05 to test for significance of changes compared to calibrator [cal] (asterisk denotes significant difference). Brk, bark; Hex, hexoses; Mal, maltose; RFO, raffinose-oligosaccharide family sugars; Snk lf, sink leaf; Src lf, source leaf; SuAlc, sugar alcohols; Suc, sucrose; Wd, wood.
Mentions: After the localization of FeSUT1 in phloem cells, environmental conditions that might influence FeSUT1 expression were analysed. Sugar and sugar alcohol contents as well as mRNA levels of FeSUT1 in different tissues of F. excelsior during different seasons were measured. The overall sugar and sugar alcohol contents were highest in bark [up to 500 µmol g−1 fresh weight (FW)] and wood in winter (Fig. 4A). Because data for sugar content and SUT expression refer to FW, and wood contains less symplast per gram FW than bark or leaves, the values for wood would be even higher if the data referred to the symplast. However, values were given per gram FW to ensure comparability with other published data (e.g. Ferner et al., 2012). In the stem tissues the main sugars were sucrose, hexoses, and RFOs (Fig. 4A). Mannitol was by far the dominant sugar alcohol (more than 90% at the total content of sugar alcohols; data not shown). In spring, sugar and sugar alcohol contents were much lower (below about 80 µmol g−1 FW) in all tissues (bark, wood, sink leaves, and source leaves). Sink leaves and source leaves were defined by size and weight. ‘Source leaves’ in spring were identified as those 80–100% of the size and weight of mature leaves in summer, whereas ‘sink leaves’ had only about 10% of those values. In summer, sugar and sugar alcohol contents in bark and wood were higher than in spring (Fig. 4A) whereas the contents in source leaves were similar or slightly lower.

Bottom Line: The localization and expression pattern point towards functions of FeSUT1 in phloem loading of sucrose as well as in sucrose retrieval.The elevated expression level of FeSUT1 indicated an increased apoplastic carbon export activity from the leaves during spring and late autumn.It is hypothesized that the importance of apoplastic loading is high under low-sucrose conditions and that the availability of two different phloem-loading mechanisms confers advantages for temperate woody species like F. excelsior.

View Article: PubMed Central - PubMed

Affiliation: Molekulare Pflanzenforschung/Pflanzenbiochemie (Botanik), Bergische Universität Wuppertal, Gaußstraße 20, D-42119 Wuppertal, Germany.

No MeSH data available.


Related in: MedlinePlus