The present invention relates to a method for producing heterologous glycosylated proteins in non-animal eukaryotic cells such as in transformed bryophyte, yeast, ciliate or algae cells. In particular, the method relates to a method for producing glycosylated proteins comprising animal glycosylation patterns--comprising sialic acid residues--, such as pharmaceutical proteins for use in mammals, e.g. humans, in bryophyte cells such as those of Physcomitrella patens, the genetic material required therefore, such as DNA and RNA, vectors, host cells, methods of introducing genetic material there into, and uses thereof. Furthermore, the present invention relates to novel polypeptides and proteins obtained by the method according to the invention. Moreover, the present invention provides a method of producing sialic acid or CMP-sialic acid in a transformed non-mammalian eukaryotic cell, tissue or organism.