EXPRESSION IN ANTHERS OF 2 GENES ENCODING BRASSICA-OLERACEA TRANSMEMBRANE CHANNEL PROTEINS

Screening of an anther cDNA expression library resulted in the isolati on of two almost identical cDNA clones, termed mipA and mipB, showing homology with sequences encoding transmembrane channel proteins from t he MTP family. Both clones were expressed in several tissues, but not in pollen. MipA was preferentially expressed in the surrounding sporop hytic tissues of stamens. Anthers subjected to drought were induced to accumulate even more mip transcripts, which was entirely due to highe r mipA gene expression. On basis of isolation procedures, sequence hom ology and drought inducibility of mipA we conclude that the encoded pr oteins probably are constituents of the pollen coat and are aquaporins .