Using the cDNA-AFLP method, we have isolated a transcript-derived fragment (TDF) which shows a differential expression pattern during tuber organogenesis of Solanum tuberosum L. The TDF was used to isolate a cDNA clone carrying a 1.5 kb insert and potentially coding for a 32.5 kDa peptide which, by homology, represents a potato homologue of an alpha-snap gene and has been designated Stsnap. Northern analysis showed that the Stsnap gene is expressed in actively dividing tissues throughout the potato plant. Analysis of genomic DNA from potato revealed that the Stsnap gene is likely to be a single-copy gene. The expression of antisense Stsnap cDNA under the control of the CaMV 35S promoter results in plants with an altered morphology such as curled leaves. Several of these transgenic lines also display cellular and developmental abnormalities with distinct changes in assimilate transport including accumulation of starch and soluble sugars in source leaves. We argue that these findings are consistent with the hypothetical function of the StSNAP gene product in vesicle targeting and fusion during plant development.