AtSTP11, a pollen tube-speci.pdfVIP

ORIGINAL ARTICLE Alexander Schneidereit ? Joachim Scholz-Starke Norbert Sauer ? Michael Bu?ttner AtSTP11, a pollen tube-specific monosaccharide transporter in Arabidopsis Received: 3 June 2004 / Accepted: 7 October 2004 / Published online: 24 November 2004
Springer-Verlag 2004 Abstract Pollen development, as well as pollen germi- nation and pollen tube growth, requires a highly regu- lated supply of sugars. In this paper we describe the molecular, kinetic, and physiological characterization of AtSTP11, a new member of the H+/monosaccharide transporter family in Arabidopsis thaliana (L.) Heynh. Heterologous expression in yeast (Saccharomyces cere- visiae) showed that AtSTP11 is a high-affinity (Km=25 lM), broad-spectrum, and uncoupler-sensitive monosaccharide transporter of the plasma membrane. In reverse transcription–polymerase chain reaction analyses we found that AtSTP11 expression is restricted to flowers. Furthermore, AtSTP11-promoter::GFP plants revealed that AtSTP11 expression is only found in pollen tubes. Using a specific antibody we could also detect the AtSTP11 protein exclusively in pollen tubes but not in other flower tissues or in pollen grains of any developmental stage. These results suggest that the newly identified AtSTP11 transporter plays a role in the supply of monosaccharides to growing pollen tubes. Keywords Arabidopsis ? AtSTP11 ? Glucose transport Monosaccharide transporter ? Pollen tube Abbreviations: AtSTP Arabidopsis thaliana sugar transport protein ? GFP Green fluorescent protein ? RT–PCR Reverse transcription–polymerase chain reaction Introduction Pollination is an essential step during sexual reproduc- tion in higher plants in which the pollen tube delivers the male sperm cells to the ovule for fertilization. The elongation of pollen tubes in the pistil is among the fastest growth processes in plants and thus requires an optimal supply of nutrients. Since pollen is a photo- synthetically inactive ‘sink’, carbohydrates have to be impo