DIP - A MEMBER OF THE MIP FAMILY OF MEMBRANE-PROTEINS THAT IS EXPRESSED IN MATURE SEEDS AND DARK-GROWN SEEDLINGS OF ANTIRRHINUM-MAJUS

DiP,a gene from Antirrhinum majus, which encodes a protein with striki ng homology to other integral membrane proteins, was cloned. The gene was specifically expressed in mature seeds and during seedling germina tion, particularly in cotyledons of seedlings grown in the dark. The d educed product, called DiP, for dark intrinsic protein, shows strong h omology with the MIP family of channel transporters which include; the bovine major intrinsic protein (MIP), the Escherichia coli glycerol f acilitator (GlpF), the peribacteroid nodulin-26 (Nod26), and the tonop last protein from kidney bean (TIP). DiP is most similar to other plan t members of this family, and in particular to the tobacco protein Tob RB7 which is expressed specifically in roots. However, the expression pattern of diP suggests that its product is functionally more similar to the tonoplast intrinsic protein from kidney bean since it is most h ighly expressed in the cotyledons of germinating seedlings, before the cells undergo expansion growth and become photosynthetic.