The AtSUC1 sucrose carrier may represent the osmotic driving force for anther dehiscence and pollen tube growth in Arabidopsis

The Arabidopsis AtSUC1 protein has previously been characterized as a plasm a membrane H+-sucrose symporter. This paper describes the sites of AtSUC1 g ene expression and AtSUC1 protein localization and assigns specific functio ns to this sucrose transporter in anther development and pollen tube growth . RNase protection assays revealed AtSUC1 expression exclusively in floral tissue, which was confirmed by analyses of AtSUC1 promoter-beta-glucuronida se (GUS) plants. In situ hybridizations identified AtSUC1 expression in ant her connective tissue, in funiculi and in fully developed pollen grains. In direct immunofluorescence analyses with anti-AtSUC1 antiserum confirmed AtS UC1 protein localization in the connective tissue and funiculi. In mature p ollen grains, however, despite high AtSUC1 mRNA levels no AtSUC1 protein wa s found. Only after pollination of stylar papillae was AtSUC1 protein detec ted inside the pollen and later inside the growing pollen tubes, suggesting a translation of pre-existing AtSUC1 mRNA after pollination. Pollen germin ation analyses underlined the important role of sucrose for pollen tube gro wth. The data presented suggest a role of AtSUC1 in the controlled dehiscen ce of Arabidopsis anthers. It is postulated that an important function of A tSUC1 is the cell-specific modulation of water potentials.