Norbert Sauer

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A version of Dirichlet's box argument asserts that given a positive integer a and any a2 +1 objects x0 , x1 , . . ., xa 2, there are always a+1 distinct indices v (0 < v < a 2) such that the corresponding ad-1 objects x,, are either all equal to each other or mutually different from each other . This proposition can be restated as follows . Let N be an(More)
Macromolecular trafficking within the sieve element-companion cell complex, phloem unloading, and post-phloem transport were studied using the jellyfish green fluorescent protein (GFP). The GFP gene was expressed in Arabidopsis and tobacco under the control of the AtSUC2 promoter. In wild-type Arabidopsis plants, this promoter regulates expression of the(More)
An important, most likely essential step for the long distance transport of sucrose in higher plants is the energy-dependent, uncoupler-sensitive loading into phloem cells via a sucrose-H+ symporter. This paper describes functional expression in Saccharomyces cerevisiae of two cDNAs encoding energy-dependent sucrose transporters from the plasma membrane of(More)
Leaves undergo a sink-source transition during which a physiological change occurs from carbon import to export. In sink leaves, biolistic bombardment of plasmids encoding GFP-fusion proteins demonstrated that proteins with an Mr up to 50 kDa could move freely through plasmodesmata. During the sink-source transition, the capacity to traffic proteins(More)
In order to understand sucrose transport in developing seeds of cereals at the molecular level, we cloned from a caryopses library two cDNAs encoding sucrose transporters, designated HvSUT1 and HvSUT2. Sucrose uptake activity was confirmed by heterologous expression in yeast. Both transporter genes are expressed in maternal as well as filial tissues. In a(More)
A cDNA for the Arabidopsis STP4 gene (for sugar transport protein 4) was isolated, and the properties of the encoded protein were studied in Schizosaccharomyces pombe. The STP4 monosaccharide H+ symporter is composed of 514 amino acids and has a calculated molecular mass of 57.1 kD. RNA gel blot analyses revealed that STP4 is expressed primarily in roots(More)
To analyze sugar transport processes during seed development of fava bean, we cloned cDNAs encoding one sucrose and one hexose transporter, designated VfSUT1 and VfSTP1, respectively. sugar uptake activity was confirmed after heterologous expression in yeast. Gene expression was studied in relation to seed development. Transcripts were detected in both(More)