Disclosed is a substantially purified, recombinant, synthetic or isolated nucleic acid encoding 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 sequence shown in SEQ ID NO: 1 (b) the complement of the sequence recited in (a) (c) a sequence antisense to the sequences recited in (a) and (b) (d) functionally active fragments and variants of the sequences recited in (a), (b) and (c) having at least approximately 80% identity to the relevant part of the sequence recited in (a), (b) or (c) and having a size of at least 30 nucleotides and (e) interfering RNA (RNAi) derived from the sequences recited in (a) and (b). Further disclosed is a substantially purified, recombinant, synthetic or isolated apyrase polypeptide from a Lolium species, wherein said polypeptide includes an amino acid sequence selected from the amino acid sequence shown in SEQ ID NO: 2, and functionally active fragments and variants thereof having at least approximately 80% identity to the relevant part of SEQ ID NO: 2 and having a size of at least 20 amino acids.
