There is described herein a plant cell comprising: (i) a polynucleotide comprising, consisting or consisting essentially of a sequence having at least 95% sequence identity to SEQ ID NO: 1 or SEQ ID NO: 3 or SEQ ID NO: 9 or SEQ ID NO: 11 or SEQ ID NO: 17 or SEQ ID NO: 19 or SEQ ID NO: 21 or SEQ ID NO: 23; or a polynucleotide comprising, consisting or consisting essentially of a sequence having at least 80% sequence identity to SEQ ID NO: 5 or SEQ ID NO: 7 or SEQ ID NO: 13 or SEQ ID NO: 15; (ii) a polypeptide encoded by the polynucleotide set forth in (i); (iii) a polypeptide comprising, consisting or consisting essentially of a sequence having at least 94% sequence identity to SEQ ID NO: 2; or at least 93% sequence identity to SEQ ID NO: 4; or least 95% sequence identity to SEQ ID NO: 6; or at least 96% sequence identity to SEQ ID NO: 8; or at least 93% sequence identity to SEQ ID NO: 10 or SEQ ID NO: 12; or at least 95% sequence identity to SEQ ID NO: 14; or at least 96% sequence identity to SEQ ID NO: 16; or at least 89% sequence identity to SEQ ID NO: 18; or at least 92% sequence identity to SEQ ID NO: 20; or at least 93% sequence identity to SEQ ID NO: 22; or at least 94% sequence identity to SEQ ID NO: 24; or (iv) a construct, vector or expression vector comprising the isolated polynucleotide set forth in (i), wherein said plant cell comprises at least one modification which modulates the expression or activity of the polynucleotide or the polypeptide as compared to a control plant cell in which the expression or activity of the polynucleotide or polypeptide has not been modified.