A novel zinc finger transcription factor linked to salt tolerance in alfalfa

Selection for salt tolerance in alfalfa cell lines is accompanied by constitutive and salt induced changes in mRNA accumulation. The plants regenerated from the salt-tolerant cell lines show heritable salt tolerance through seed, indicating that the cellular mechanisms of salt tolerance also function at the whole plant level. We have cloned and investigated the function of two of these salt-induced transcripts. One of these, (Aff/nî), encodes a putative zinc finger (C4,HC3) transcription factor. Another one, (MsPRP2), encodes a proline rich cell wall protein with a hydrophobic carboxy terminus. Both Alfin 1 and MsPRPZ show salt dependent mRNA accumulation in salt-tolerant culture and roots of the regenerated salt-tolerant plants. To investigate the functions of these genes we have expressed Alfin 1 in bacteria and we have cloned and sequenced the promoter region of MsPRP2. We have demonstrated the DNA binding properties of Alfinl recombinant protein and have cloned the DNA binding sequences by four rounds of selection and PCR amplification. The cloned sequences show a GC rich consensus sequence. Similar sequences are found in promoter fragments of MsPRP2 that show specific binding of recombinant Alfinl. The effect cX Allini over-expression on MsPRP2 is being monitored in transgenic alfalfa.