UASt regulates expression of the N-terminal 10 amino-acid residues of SP (SPn) followed by a GFP(V63A.S65T) tag. The 19aa signal sequence of SP is present at the N-terminus (so that the product is secreted) and 5-7 amino-acid-long spacers are placed between the GFP(V63A.S65T) and SP fragments.