Genome-wide analysis of stress-responsive genes and alternative splice variants in Arabidopsis roots under osmotic stresses

The shoots and roots of a plant respond differently to osmotic stress, as they have distinct functions and anatomical structures. Under conditions of high solute concentration, such as in saline soils or drought, water uptake by the roots is reduced, resulting in cellular dehydration. In this study, we performed transcriptional profiling of roots of Arabidopsis under osmotic stress conditions such as high salinity and drought using mRNA-Seq for the assessment of gene expression changes in roots of Arabidopsis. mRNA-Seq analysis showed that many differentially expressed genes showed differential expressions under both salt stress and drought stress conditions in roots and were distinct from aerial parts. We confirmed 68 transcription factor genes which is involved in osmotic stress signal transduction in roots and are connected tightly. Interestingly, well-known ABA-dependent and/or -independent osmotic stress-responsive genes were less increased in roots, indicating that osmotic stress response in roots might be regulated by stress pathways other than well-known pathways. We identified 26 osmotic stress-responsive genes, which have alternative splicing variant isoforms, showed distinct expression in roots under osmotic stress conditions from the mRNA-Seq analysis. Quantitative RT-PCR confirmed that alternative splicing variants, such as ANNAT4, MAGL6, TRM19, and CAD9, have differential expressions in roots under osmotic stress conditions, indicating that alternative splicing is an important regulatory mechanism in osmotic stress response in roots. Taken together, our study suggest that many transcription factor families are involved in osmotic stress response in roots and tightly connected each other. In addition, alternative splicing and function of alternative splicing variant isoforms are also important in osmotic stress response in roots. To understand the alternative splicing mechanism in roots, further study is necessary. Overall design: Differentially expressed genes between in whole seedlings and in roots under NaCl or mannitol treatment at 10 days after germination under SD conditions (8-h-light and 16-h-dark cycle) were explored in whole genome level.