Splice variants of superoxide dismutases in rice and their expression profiles under abiotic stresses

Authors: SAINI, AJAY - Oklahoma State University; Rohila, Jai; GOVINDAN, GANESAN - Oklahoma State University; LI, YONG-FONG - Oklahoma State University; SUNKAR, RAMANJULU - Oklahoma State University

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2021
Publication Date: 4/13/2021
Citation: Saini, A., Rohila, J.S., Govindan, G., Li, Y., Sunkar, R. 2021. Splice variants of superoxide dismutases in rice and their expression profiles under abiotic stresses. International Journal of Molecular Sciences. https://doi.org/10.3390/ijms22083997.
DOI: https://doi.org/10.3390/ijms22083997

Interpretive Summary: The rice plant continually generates reactive oxygen species (ROS) molecules which play important roles in molecular signaling for the plant’s growth and developmental processes. The unused ROS in plant cells is degraded by superoxide dismutases (SODs) molecules. However, under abiotic stress conditions, the ROS molecules start accumulating in various cellular compartments, such as mitochondria, chloroplast, and cause cell death. Overaccumulation of ROS is partially due to reduced or inefficient activity of SOD genes. The rice genome encodes seven SOD genes but by minor genomic rearrangements in the DNA the plant can create 15 different forms from these seven genes; commonly known as slice variants (SV). Comprehensive knowledge of these SVs becomes crucial to better understand cell death mechanisms under abiotic stress conditions and for developing stress resilient rice cultivars. In this study, we conducted a detailed analysis of the DNA structure of the seven rice SOD genes and their predicted SVs. When rice seedlings were grown under abiotic stressed conditions, some patterns in the location and timing of the products of these SVs were detected. In addition, some SVs showed opposite profiles in shoot and root tissues suggesting a unique role for these SVs in different parts of the rice plant. Overall, this study improved our understanding of how SVs may trigger responses to abiotic stress in rice plants.

Technical Abstract: 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. Rice genome harbors seven SOD genes (CSD1, CSD2, CSD3, CSD4, FSD1, FSD2 and MSD) that encode seven constitutive transcripts. Of these, five SOD genes (CSD2, CSD3, CSD4, FSD1 and MSD) utilizes alternative splicing (AS) strategy and generate seven additional splice varinats (SVs), i.e., three for CSD3, and one each for CSD2, CSD4, FSD1 and MSD. The exon-intron organization of these SVs revealed variations in number and length of the exons and/or UTRs. We determined the expression patterns of SVs along with their consititutive forms of SODs in rice seedlings exposed to salt, osmotic, cold and oxidative stresses as well as copper deprivation. The results revealed that all of the seven SVs were transcriptionally active both in roots and shoots. When compared to their corresponding constitutive transcripts, the profiles of five SVs were almost similar while opposite profiles for two specific SVs (CSD3-SV4 and MSD-SV2) were consistently observed under stress conditions. Taken together, the present study provide a comprehensive analysis of the SVs of SODs and their responses to stress conditions in shoots and roots of rice seedlings.