One of two tandem Arabidopsis genes homologous to monosaccharide transporters is senescence-associated

A gene designated SFP1, which is similar to major facilitator superfamily m onosaccharide transporters, is induced during leaf senescence. Genomic sequ ence analysis identified a second highly similar and closely linked gene, S FP2, suggesting that SFP1 and SFP2 may have arisen through a recent duplica tion event. However, RNA gel-blot analyses and histochemical localization o f a reporter gene activity in transgenic plants show that SFP1 and SFP2 are differentially regulated and that only SFP1 is induced during leaf senesce nce. The increase in SFP1 gene expression during leaf senescence is paralle led by an accumulation of monosaccharides. Possible roles for SFP1 in sugar transport during leaf senescence are discussed.