Analysis of the cDNAs of granule-bound starch synthase I (GBSSI) in sweet potato indicated that six types of GBSSI were expressed in the tuberous root, and that the poly(A) sites in GBSSI were highly heterogeneous. Several poly(A) sites were located within or downstream of the polymorphic TA repeat. The GBSSI gene has a 23-nucleotide A-rich sequence in the 3′ untranslated region, and we believe that the main near-upstream elements of the poly(A) signal are included in this sequence.
