Identification of mRNAs and proteins in higher plants using probes from the Band 3 anion transporter of mammals

Band 3 is a well characterized ion transporter in mammalian cells. To determine if Zea mays expressed Band 3-related polypeptides, polyclonal antibodies to a 13-amino acid sequence at the carboxyl terminal end of the membrane domain of the mouse Band 3 anion transporter was used in immunoblot studies. This antiserum detected three classes of polypeptides from maize roots. The polypeptides had apparent molecular masses of 43, 46 and 59 kDa and appeared to be integral membrane components associated with various cellular membranes including the plasma membrane. Maize genomic DNA did not contain sequences that cross-hybridized with the mouse cDNA encoding the C-terminal membrane domain of Band 3. However, an oligonucleotide corresponding to a portion of the 13-amino acid sequence used for antibody preparation detected mRNAs from both monocotyledonous and dicotyledonous plants. The maize root and leaf mRNAs that were detected were 1.75, 1.45, and 0.88 kb in size. The levels of the 1.75- and 1.45 kb mRNAs in maize roots did not change dramatically in response to nitrate; however, the O.88kb transcript levels increased in response to nitrate. Using the ³²P-labelled Band 3 oligonucleotide, a partial cDNA clone (λB3-2758) encoding a 0.88 kb transcript was isolated. The abundance of the B3-2758 and nitrate reductase transcripts increased markedly in response to nitrate in an amino acid-grown maize cell line and was well correlated with the induction of nitrate transport.