Molecular cloning and characterization of salt responsive genes in rice (Oryza sativa)

Differential screening was performed on a cDNA library made from RNAs isolated from rice seedlings (variety TSA 2), grown in water culture with 3 h osmotic shock (150 mmol/L NaCl). Sixteen cDNA clones showing preferential hybridization to RNA from salt shocked seedlings were isolated. Three clones encoding salt responsive protein were selected by Northern hybridization study. One of the clones OSSRI represented a gene that is expressed at high levels during 24 h NaCl treatment. The DNA sequence analysis of OSSRI indicated a similarity to the deduced amino acid sequence of inositol phosphate kinase like protein of Arabidopsis thaliana. Another clone OSSRII showed identity to the photosystem II reaction center W protein of Arabidopsis thaliana. The clone OSSRIII was highly similar to cysteine proteinase inhibitor which is strongly associated with a chilling inducible and drought tolerant protein. Hybridization of the clone OSSRI to genomic DNA digested with EcoR1, EcoRV, Hind III, and Sal1 indicated that a single copy of the gene encoded the salt inducible transcript. RNA blot hybridization showed that mRNA of 1.3, 1.0, 0.9 kb for the clones OSSRI, OSSRII and OSSRIII, respectively, accumulated over time up to 24 h.