Splice Variants of Superoxide Dismutases in Rice and Their Expression Profiles under Abiotic Stresses.

The superoxide dismutases (SODs) play vital roles in controlling cellular reactive oxygen species (ROS) that are generated both under optimal as well as stress conditions in plants. The rice genome harbors seven SOD genes (, , , , , and ) that encode seven constitutive transcripts. Of these, five (, , , and ) utilizes an alternative splicing (AS) strategy and generate seven additional splice variants () or mRNA variants, i.e., three for , and one each for , , and . The exon-intron organization of these revealed variations in the number and length of exons and/or untranslated regions (UTRs). We determined the expression patterns of along with their constitutive forms of in rice seedlings exposed to salt, osmotic, cold, heavy metal (Cu) stresses, as well as copper-deprivation. The results revealed that all seven were transcriptionally active in both roots and shoots. When compared to their corresponding constitutive transcripts, the profiles of five were almost similar, while two specific ( and ) differed significantly, and the differences were also apparent between shoots and roots suggesting that the specific SVs are likely to play important roles in a tissue-specific and stress-specific manner. Overall, the present study has provided a comprehensive analysis of the SVs of SODs and their responses to stress conditions in shoots and roots of rice seedlings.