Minisymposium 19:
Abs #
33003: New Arabidopsis monosaccharide transporters (AtSTPs) expressed in reproductive flower parts
We have identified a family of 14 monosaccharide transporters (AtSTPs) in Arabidopsis, most of them showing sink-specific expression profiles and the ability to transport a broad range of different monosaccharides as substrate. Here we present data on the characterization of three new members, AtSTP9, AtSTP11 and AtSTP14. which are expressed in reproductive parts of the flower. Besides AtSTP2, AtSTP4 and AtSTP6 which have previously been identified in pollen, we could localize two additional transporters AtSTP9 and AtSTP11 in this reproductive cell type using promoter/reporter plants and specific antibodies. Heterologous expression of these transporters in yeast revealed, that AtSTP11 transports a variety of monosaccharides while AtSTP9 is the first AtSTP specific for glucose. Single knock-out plants for AtSTP6 and AtSTP9 do not affect pollen ripening, pollen germination or fertilization indicating a functional overlap. Currently we are in the process of generating multiple knock-out plants to elucidate the role of AtSTPs in pollen development and germination.
AtSTP14 is the first Arabidopsis carrier which does not accept glucose as a substrate but instead transports galactose and with lower rates xylose, both being cell wall components. Preliminary RT-PCR data indicate that AtSTP14 is expressed in leaves and siliques while promoter/GFP-plants only show reporter-expression in the seed endosperm. We are currently generating an AtSTP14-specific antibody to verify these data and exactly localize AtSTP14 in both cell types. Furthermore, we have isolated a knock-out line of AtSTP14 by screening the Madison-collection. Since this knock-out mutant is not affected in seed development or germination we have to assume a similar redundancy of AtSTPs in seeds as found in pollen.
