Disclosed is a substantially purified, recombinant, synthetic or isolated apyrase polypeptide from a Trifolium species, wherein said polypeptide includes an amino acid sequence selected from the amino acid sequences shown in SEQ ID NOs: 4 and 6, and functionally active variants thereof having at least approximately 90% identity to SEQ ID NO: 4 or 6, respectively. Further disclosed is a substantially purified, recombinant, synthetic or isolated nucleic acid from a Trifolium species, said nucleic acid or nucleic acid fragment encoding an amino acid sequence of an apyrase polypeptide, or complementary or antisense to a nucleic acid sequence encoding an apyrase polypeptide, wherein said nucleic acid includes a nucleotide sequence selected from the group consisting of (a) the sequences shown in SEQ ID NOs: 3 and 5 (b) the complements of the sequences recited in (a) (c) sequences antisense to the sequences recited in (a) and (b) (d) functionally active variants of the sequences recited in (a), (b) and (c) having at least approximately 90% identity to the sequence recited in (a), (b) or (c) and (e) interfering RNA (RNAi) derived from the sequences recited in (a) and (b).
