Characterization and expression pattern of an abscisic acid and osmotic stress responsive gene from rice

Identification and characterization of salt responsive genes is an initial step in understanding the adaptive responses to salinity. We report the cha racterization and expression pattern of an abscisic acid (ABA) and osmotic stress responsive gene from rice which shows sequence similarity with the A sr (ABA, stress and ripening inducible) genes identified in several species . A partial cDNA for the Oryza saliva Asr1 (OsAsr1) was identified from a c DNA library constructed from salt stressed tissues of Pokkali, a salt toler ant rice variety by sequence homology. Subsequently, the cDNA encoding the complete polypeptide was cloned by PCR amplification from the same cDNA lib rary. The OsAsr1 sequence encodes a hydrophilic protein with a molecular we ight of 15.4 kDa and has the conserved regions of the ASR homologs. OsAsr1 hybridizes to a similar to 0.8 kb transcript which is constitutively expres sed; its levels in the shoot are up-regulated by exogenous application of A BA and osmotic stress imposed by mannitol and salt. Further, the salt induc tion is transient, increasing at least up to 6 h and reduced within 24 h of stress. Southern and Blast analysis suggests that the Asr genes form-a gen e family of at least two members in rice. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.