A plant cell or plant containing a foreign nucleic acid molecule stably integrated into its genome, wherein the foreign nucleic acid molecule is coding for a protein having the activity of a glutamine:fructose 6-phosphate amidotransferase (GFAT), wherein the foreigen nucleic acid molecule codes for a protein having the activity of a glutamine:fructose 6-phosphate amidotransferase of isoform II (GFAT-2) or a protein having the activity of a bacterial glutamine:fructose 6-phosphate amidotransferase (bacterial GFAT) and wherein the plant cell or plant has a content of N-acetylated glucosamine derivatives of at least 2 μmol per gram of fresh weight where the foreign nucleic acid molecule coding for a protein having the activity of a GFAT-2 or coding for a protein having the activity of a bacterial GFAT is selected from the group consisting of a) nucleic acid molecules coding for a protein having the amino acid sequence given under SEQ ID NO 7 (GFAT-2) or a protein having the amino acid sequence given under SEQ ID NO 9 (bacterial GFAT); b) nucleic acid molecules coding for a protein whose sequence is at least 60%, identical to the amino acid sequence shown under SEQ ID NO 7 (GFAT-2) or under SEQ ID NO 9 (bacterial GFAT); c) nucleic acid molecules comprising the nucleotide sequence shown under SEQ ID NO 6 (GFAT-2) or under SEQ ID NO 8 (bacterial GFAT) or under SEQ ID NO 10 (bacterial GFAT) or a sequence complementary thereto; d) nucleic acid molecules which are at least 60% identical to the nucleic acid sequences shown under a) or c); e) nucleic acid molecules which hybridize under stringent conditions with at least one strand of the nucleic acid sequences described under a) or c); f) nucleic acid molecules whose nucleotide sequence differs from the sequence of the nucleic acid molecules mentioned under a) or c) owing to the degeneracy of the genetic code and g) nucleic acid molecules which are fragments, allelic variants and/or derivatives of the nucleic acid molecules mentioned under a), b), c), d), e) or f). a) nucleic acid molecules coding for a protein having the amino acid sequence given under SEQ ID NO 7 (GFAT-2) or a protein having the amino acid sequence given under SEQ ID NO 9 (bacterial GFAT); b) nucleic acid molecules coding for a protein whose sequence is at least 60%, identical to the amino acid sequence shown under SEQ ID NO 7 (GFAT-2) or under SEQ ID NO 9 (bacterial GFAT); c) nucleic acid molecules comprising the nucleotide sequence shown under SEQ ID NO 6 (GFAT-2) or under SEQ ID NO 8 (bacterial GFAT) or under SEQ ID NO 10 (bacterial GFAT) or a sequence complementary thereto; d) nucleic acid molecules which are at least 60% identical to the nucleic acid sequences shown under a) or c); e) nucleic acid molecules which hybridize under stringent conditions with at least one strand of the nucleic acid sequences described under a) or c); f) nucleic acid molecules whose nucleotide sequence differs from the sequence of the nucleic acid molecules mentioned under a) or c) owing to the degeneracy of the genetic code and g) nucleic acid molecules which are fragments, allelic variants and/or derivatives of the nucleic acid molecules mentioned under a), b), c), d), e) or f).