Mougeotia scalaris is a filamentous streptophyte alga renowned for light-inducible plastid rotation and microtubule-dependent polarity establishment. As a first step toward transgenic approaches we determined the 5,825 base pair genomic sequence encoding the α-tubulin1 gene (MsTUA1) of M. scalaris (strain SAG 164.80). The subcloned MsTUA1 promoter facilitated strong transgene expression in M. scalaris and tobacco leaf cells, as shown by particle bombardment and the subsequent visualization of expressed fluorescent protein markers. Our results provide a route for the genetic transformation of the filamentous streptophyte alga M. scalaris based on the endogenous TUA1 promoter.