Production of milk oligosaccharides in plants

A method of producing a mammalian milk oligosaccharide (MMO) in a plant or plant part, comprising growing a plant comprising and expressing a recombinant MMO biosynthetic pathway sufficient to produce the MMO, wherein the pathway produces the MMO in the plant or plant part, wherein the pathway comprises recombinant enzymes:

• a β1-4 galactosyltransferase (β1-4-GalT), which glycosylates glucose using UDP-galactose to make lactose;
• and
• a β1-3 N-acetylglucosaminyltransferase (1-3-GlcNAc), which generates lacto-N-triose (LNTII) through the transfer of GlcNAC from UDP-GlcNAc to the galactose in the lactose;
• and at least one of:
• a β1-3-galactosyltransferase (β1-3-GalT) and a β1-4-galactosyltransferase (β1-4-GalT), which converts the LNTII to lacto-N-tetraose (LNT) and lacto-N-neotetraose (LNnT), respectively,
• wherein the plant is tobacco.