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          Institute: MPI für molekulare Pflanzenphysiologie     Collection: Publikationen Pflanzenphysiologie     Display Documents



ID: 127561.0, MPI für molekulare Pflanzenphysiologie / Publikationen Pflanzenphysiologie
The sucrose transporter StSUT1 localizes to sieve elements in potato tuber phloem and influences tuber physiology and development
Authors:Kuhn, C.; Hajirezaei, M. R.; Fernie, A. R.; Roessner-Tunali, U.; Czechowski, T.; Hirner, B.; Frommer, W. B.
Date of Publication (YYYY-MM-DD):2003
Title of Journal:Plant Physiology
Volume:131
Issue / Number:1
Start Page:102
End Page:113
Review Status:not specified
Audience:Not Specified
Abstract / Description:The sucrose (Suc) H+-cotransporter StSUT1 from potato (Solanum tuberosum), which is essential for long-distance transport of Suc and assumed to play a role in phloem loading in mature leaves, was found to be expressed in sink tubers. To answer the question of whether SUT1 serves a function in phloem unloading in tubers, the promoter was fused to gusA and expression was analyzed in transgenic potato. SUT1 expression was unexpectedly detected not in tuber parenchyma but in the phloem of sink tubers. Immunolocalization demonstrated that StSUT1 protein was present only in sieve elements of sink tubers, cells normally involved in export of Suc from the phloem to supply developing tubers, raising the question of the role of SUT1 in tubers. SUT1 expression was inhibited by antisense in transgenic potato plants using a class I patatin promoter B33, which is primarily expressed in the phloem of developing tubers. Reduced SUT1 expression in tubers did not affect aboveground organs but led to reduced fresh weight accumulation during early stages of tuber development, indicating that in this phase SUT1 plays an important role for sugar transport. Changes in Suc- and starch-modifying enzyme activities and metabolite profiles are consistent with the developmental switch in unloading mechanisms. Altogether, the findings may suggest a role of SUT1 in retrieval of Suc from the apoplasm, thereby regulating the osmotic potential in the extracellular space, or a direct role in phloem unloading acting as a phloem exporter transferring Suc from the sieve elements into the apoplasm. [References: 61] 61
Free Keywords:Yeast-derived invertase. Solanum-tuberosum. Apoplastic expression.
; Plasma-membrane. Tobacco-leaves. Spinach leaves. Sink strength.
; Plants. Gene. Trafficking.
; Plant Sciences in Current Contents(R)/Agricultural, Biology &
; Environmental Sciences
; Animal & Plant Sciences in Current Contents(R)/Life Sciences.
; 2003 week 09
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für molekulare Pflanzenphysiologie/Molekulare Physiologie/AG Willmitzer/Fernie
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