Molecular Mechanism Of A Spliceosome Component SmEb Regulating Salt Tolerance In Arabidopsis

With the increasing scarcity of freshwater resources,the salt stress produced by soil salinity inhibits plant growth and development,which seriously threatens agricultural production and food security.Ionic toxicity(mainly Na~+toxicity),osmotic stress,and oxidative stress due to salt stress often impair energy metabolism and photosynthetic efficiency.In the long-term evolution,plants have evolved a series of mechanisms to cope with salt stress,including reducing oxidative damage and activating the Na~+signaling pathway.In eukaryotes,pre-m RNA splicing,as a post-transcriptional regulation,largely contributes to the enrichment of the transcriptome and proteome and contributes to plant responses to environmental stresses.In this study,we found that a shearsome core component,Sm protein-coding gene SmEb,is involved in plant responses to salt stress.The deletion mutant of Arabidopsis thaliana Sm Eb showed decreased resistance to salt stress,indicating that Sm Eb is regulating plant tolerance to salt stress.Our RNA-seq data suggest that selective splicing of pre-m RNA in some Arabidopsis salt stress response genes relies on Sm Eb.Among them,the erroneous splicing variant RCD1.2 of RCD1(Radical-induced cell death 1)pre-m RNA in Arabidopsis plants was significantly higher than that of Col-0 in smeb deletion mutants under salt stress,resulting in a significant decrease in the ratio of RCD1.1 to RCD1.2 in smeb deletion mutants compared with wild-type Col-0.In addition,we found that RCD1.1 is located in the nucleus of the stressed body and can interact with the transcription factor DREB2s(Dehydration response element binding 2s).Although RCD1.2 is also localized in nucleially stressed bodies,its RST domain is missing and cannot interact with DREB2s.Under salt stress conditions,RCD1.1 is localized in the nucleus and cytoplasm and is able to interact with the plasma membrane-localized Na~+/H~+exchanger SOS1.Subsequently,our genetic evidence suggests that overexpression of RCD1.1 partially restores the salt-sensitive phenotype of smeb-1 deletion mutants,while RCD1.2 does not.We also found that ROS-induced cell death in the leaves of smeb-1 deletion mutants under salt stress conditions was significantly higher than that of wild type.These results suggest that RCD1.1 may be necessary to reduce salt-induced cell damage in Arabidopsis.Our results clarify the important role of spliceosome component Sm Eb in maintaining proper pre-m RNA splicing,and reveal its molecular genetic mechanism for regulating the salt stress response of Arabidopsis thaliana by maintaining proper splicing of RCD1pre-m RNA,which expands the theoretical basis of plant response to salt stress.