A minigene comprising a 494bp fragment from directly upstream of the predicted transcription start site of Syp promoter 1, the 508bp Syp-RT 5'UTR, EYFP, cDNA encoding the Syp-PT coding sequence (2013bp) and an 804bp fragment comprising the Syp-RT/Syp-RV 3'UTR plus some 3' genomic sequence.