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

Abstract

Identification and characterization of salt responsive genes is an initial step in understanding the adaptive responses to salinity. We report the characterization and expression pattern of an abscisic acid (ABA) and osmotic stress responsive gene from rice which shows sequence similarity with the Asr (ABA, stress and ripening inducible) genes identified in several species. A partial cDNA for the Oryza sativa Asr1 ( OsAsr1) was identified from a cDNA library constructed from salt stressed tissues of Pokkali, a salt tolerant rice variety by sequence homology. Subsequently, the cDNA encoding the complete polypeptide was cloned by PCR amplification from the same cDNA library. The OsAsr1 sequence encodes a hydrophilic protein with a molecular weight of 15.4 kDa and has the conserved regions of the ASR homologs. OsAsr1 hybridizes to a ∼0.8 kb transcript which is constitutively expressed; its levels in the shoot are up-regulated by exogenous application of ABA and osmotic stress imposed by mannitol and salt. Further, the salt induction 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 gene family of at least two members in rice.