The Sucrose Transporter<i>StSUT1</i>Localizes to Sieve Elements in Potato Tuber Phloem and Influences Tuber Physiology and Development,

Kühn, Christina; Hajirezaei, Mohammad‐Reza; Fernie, Alisdair R.; Roessner, Ute; Czechowski, Tomasz; Hirner, Brigitte; Frommer, Wolf B.

doi:10.1104/pp.011676

Cited by 125 publications

(107 citation statements)

References 57 publications

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“…The unloading route may differ according not only to sink types, but also to sink development, sink function, and even to growth conditions for a particular sink type, and alternative unloading pathways may exist in the sinks with symplasmically interconnecting phloem (Patrick, 1997;Roberts et al, 1997;Oparka and Turgeon, 1999;Viola et al, 2001). These observations are supported by recent research revealing that the plasmodesmal conductivity can be programmatically reduced (Baluska et al, 2001;Itaya et al, 2002) and that the transgenic expression of both apoplasmic invertase (Sonnewald et al, 1997) and sugar transporter (Harrison, 1996;Kuhn et al, 2003) may occur in tissues characterized by a predominant symplasmic phloem pathway. Because of the probable limitations due to transmembrane solute movement, apoplasmic phloem unloading is theoretically scarcely realizable in strong sinks such as meristems, seeds, and fruits (Offler and Patrick, 1993;Wang et al, 1995b).…”

supporting

confidence: 70%

Evidence for Apoplasmic Phloem Unloading in Developing Apple Fruit

et al. 2004

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The phloem unloading pathway remains unclear in fleshy fruits accumulating a high level of soluble sugars. A structural investigation in apple fruit (Malus domestica Borkh. cv Golden Delicious) showed that the sieve element-companion cell complex of the sepal bundles feeding the fruit flesh is symplasmically isolated over fruit development. 14 C-autoradiography indicated that the phloem of the sepal bundles was functional for unloading. Confocal laser scanning microscopy imaging of carboxyfluorescein unloading showed that the dye remained confined to the phloem strands of the sepal bundles from the basal to the apical region of the fruit. A 52-kD putative monosaccharide transporter was immunolocalized predominantly in the plasma membrane of both the sieve elements and parenchyma cells and its amount increased during fruit development. A 90-kD plasma membrane H 1 -ATPase was also localized in the plasma membrane of the sieve element-companion cell complex. Studies of [ 14 C]sorbitol unloading suggested that an energy-driven monosaccharide transporter may be functional in phloem unloading. These data provide clear evidence for an apoplasmic phloem unloading pathway in apple fruit and give information on the structural and molecular features involved in this process.The partitioning of sugars in economically important sink organs such as fruits or seeds is governed by several complex physiological processes, including photosynthetic rate, phloem loading in the source leaf, long-distance translocation in the phloem, phloem unloading in sink organs, postphloem transport, and metabolism of imported sugars in sink cells (Oparka, 1990;Patrick, 1997). It is now well accepted that phloem unloading plays a key role in the partitioning of photoassimilate (Fisher and Oparka, 1996;Patrick, 1997;Viola et al., 2001). The process of phloem unloading has been studied extensively over the last 20 years (for review, see Oparka, 1990;Patrick, 1997;Schulz, 1998) but still remains poorly understood. Elucidation of the cellular pathway of phloem unloading is central to this process, because, to a large extent, the unloading path determines the key transport events responsible for assimilate movement from the sieve elements (SEs) to the recipient sink cells (Fisher and Oparka, 1996;Patrick, 1997). A symplasmic phloem unloading pathway predominates in most sink tissues such as vegetative apices (Oparka et al., 1995;Patrick, 1997;Imlau et al., 1999), sink leaves (Roberts et al., 1997;Imlau et al., 1999;Haupt et al., 2001), and potato tubers that represent a typical terminal vegetative storage sink (Oparka and Santa Cruz, 2000;Viola et al., 2001). Symplasmic unloading is also efficient in the maternal tissues of developing seeds that represent a class of terminal reproductive storage sinks (Ellis et al., 1992;Patrick et al., 1995;Wang et al., 1995a;Patrick, 1997), although transfer of solutes to the apoplasm may occur at some point along the postphloem pathway (Patrick, 1997). In some cases, symplasmic unloading also occurs in elongating z...

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supporting

confidence: 70%

Evidence for Apoplasmic Phloem Unloading in Developing Apple Fruit

et al. 2004

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“…This reveals the dual function of PsSUT1, which is able to mediate both sucrose unloading and phloem loading. Indeed, many studies have found that SUT1 is expressed in both sink tissues and source tissues, and these carrier proteins are thought to play dual functions: regulating the loading in source tissues and unloading in sink tissues of photoassimilates (mainly sucrose) in apoplastic phloem transmembrane pathway (Lalonde et al, 1999;Kühn et al, 2003). For example, StSUT1 of Solanum tuberosum, which is responsible for assimilation loading, also plays an important role in tuber phloem unloading (Kühn et al, 2003).…”

Section: Discussionmentioning

confidence: 99%

“…Indeed, many studies have found that SUT1 is expressed in both sink tissues and source tissues, and these carrier proteins are thought to play dual functions: regulating the loading in source tissues and unloading in sink tissues of photoassimilates (mainly sucrose) in apoplastic phloem transmembrane pathway (Lalonde et al, 1999;Kühn et al, 2003). For example, StSUT1 of Solanum tuberosum, which is responsible for assimilation loading, also plays an important role in tuber phloem unloading (Kühn et al, 2003). SUT genes cloned from Galega officinalis (Li et al, 2011), Malus pumila (Peng et al, 2011), Triticum aestivum (Deol et al, 2013), and Leymus chinensis (Su et al, 2013) are expressed both in source leaves and sink tissues such as seeds, fruits, and stems.…”

Section: Discussionmentioning

confidence: 99%

Cloning and expression of the sucrose transporter gene PsSUT1 from tree peony leaf

Yh¹,

Guo²,

Yong³

et al. 2015

Genet. Mol. Res.

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ABSTRACT. This study reports the cloning of a sucrose transporter gene, PsSUT1, from the leaf of tree peony (Paeonia suffruticosa Lind. cv 'Huhong'). Expression patterns were examined in different organs and at different developmental stages. The full-length cDNA of PsSUT1 consisted of a 2001-bp sequence containing a 1557-bp open reading frame, encoding 519 amino acids with a conserved domain typical of the glycoside-pentoside-hexuronide superfamily. The amino acid sequence of PsSUT1 in tree peony shared high homology with that of other plants. At different developmental stages, PsSUT1 was expressed in roots, stems, leaves, and petals. Its expression level in stems was 10.9-fold higher than in petals at the flowering stage. Expression of PsSUT1 at the flowering stage was highest during flower development. The significant differences in PsSUT1 expression observed among developmental stages and organs were closely related to changes in sucrose content during flower opening. These results form the basis for further research on the molecular mechanisms of carbohydrate metabolism and transport during flower development in tree peony.

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“…The isolated fusion protein exhibited no discernible FRET, suggesting that protein stability may have been compromised. We have previously observed that within a binding protein family, only a subset may be facilely converted to working FRET sensors by simple linear fusion of chromophore variants 3 ; putative nanosensors may fail to show detectable FRET or show FRET but no ligand-dependent FRET change. SmAglE was fused in a similar manner but provided a FLIP with an extremely low starting ratio of ϳ0.7 and a sucrose-induced ratio change of only 0.05 (data not shown).…”

Section: Determining the Ligand Binding Specificity Of A Putativementioning

confidence: 99%

“…Even though much has been discovered about phloem import of sucrose, essentially nothing is known about the export from photosynthetic mesophyll cells. Although it is conceivable that the H ϩ -coupled transporters can work in reverse for exporting sucrose from the phloem in "sink" tissues, direct evidence of this as the major export route is lacking (2,3). Perhaps more importantly, the microscopic distribution of sucrose within cellular compartments is largely unknown.…”

mentioning

confidence: 99%

Conversion of a Putative Agrobacterium Sugar-binding Protein into a FRET Sensor with High Selectivity for Sucrose

Lager

Looger

Hilpert

et al. 2006

Journal of Biological Chemistry

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Glucose is the main sugar transport form in animals, whereas plants use sucrose to supply non-photosynthetic organs with carbon skeletons and energy. Many aspects of sucrose transport, metabolism, and signaling are not well understood, including the route of sucrose efflux from leaf mesophyll cells and transport across vacuolar membranes. Tools that can detect sucrose with high spatial and temporal resolution in intact organs may help elucidate the players involved. Here, FRET sensors were generated by fusing putative sucrose-binding proteins to green fluorescent protein variants. Plant-associated bacteria such as Rhizobium and Agrobacterium can use sucrose as a nutrient source; sugar-binding proteins were, thus, used as scaffolds for developing sucrose nanosensors. Among a set of putative sucrose-binding protein genes cloned in between eCFP and eYFP and tested for sugar-dependent FRET changes, an Agrobacterium sugar-binding protein bound sucrose with 4 M affinity. This FLIPsuc-4 protein also recognized other sugars including maltose, trehalose, and turanose and, with lower efficiency, glucose and palatinose. Homology modeling enabled the prediction of binding pocket mutations to modulate the relative affinity of FLIPsuc-4 for sucrose, maltose, and glucose. Mutant nanosensors showed up to 50-and 11-fold increases in specificity for sucrose over maltose and glucose, respectively, and the sucrose binding affinity was simultaneously decreased to allow detection in the physiological range. In addition, the signal-tonoise ratio of the sucrose nanosensor was improved by linker engineering. This novel reagent complements FLIPs for glucose, maltose, ribose, glutamate, and phosphate and will be used for analysis of sucrose-derived carbon flux in bacterial, fungal, plant, and animal cells.

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The Sucrose TransporterStSUT1Localizes to Sieve Elements in Potato Tuber Phloem and Influences Tuber Physiology and Development,

Cited by 125 publications

References 57 publications

Evidence for Apoplasmic Phloem Unloading in Developing Apple Fruit

Evidence for Apoplasmic Phloem Unloading in Developing Apple Fruit

Cloning and expression of the sucrose transporter gene PsSUT1 from tree peony leaf

Conversion of a Putative Agrobacterium Sugar-binding Protein into a FRET Sensor with High Selectivity for Sucrose

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