The Arabidopsis splicing regulator SR45 confers salt tolerance in a splice isoform-dependent manner
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Functions of most splice isoforms that are generated by alternative splicing are unknown. We show that two splice variants that encode proteins differing in only eight amino acids have distinct functions in a stress response.
Serine/arginine-rich (SR) and SR-like proteins, a conserved family of RNA binding proteins across eukaryotes, play important roles in pre-mRNA splicing and other post-transcriptional processes. Pre-mRNAs of SR and SR-like proteins undergo extensive alternative splicing in response to diverse stresses and produce multiple splice isoforms. However, the functions of most splice isoforms remain elusive. Alternative splicing of pre-mRNA of Arabidopsis SR45, which encodes an SR-like splicing regulator, generates two isoforms (long—SR45.1 and short—SR45.2). The proteins encoded by these two isoforms differ in eight amino acids. Here, we investigated the role of SR45 and its splice variants in salt stress tolerance. The loss of SR45 resulted in enhanced sensitivity to salt stress and changes in expression and splicing of genes involved in regulating salt stress response. Interestingly, only the long isoform (SR45.1) rescued the salt-sensitive phenotype as well as the altered gene expression and splicing patterns in the mutant. These results suggest that SR45 positively regulates salt tolerance. Furthermore, only the long isoform is required for SR45-mediated salt tolerance.
KeywordsPre-mRNA splicing SR45 Salt stress Abiotic stress Stress-responsive genes Arabidopsis Splice isoform
This research was supported by a Grant from the National Science Foundation (ABI 0743097). We thank Dr. Xiao-Ning Zhang, St. Bonaventure University, St. Bonaventure, NY for providing the seeds of complemented lines; Dr. Salah and Dr. Palusa for their help on this Project; Dr. Prasad for his comments on the manuscript. MA was supported by a Ph.D. fellowship from the government of the Kingdom of Saudi Arabia.
ASNR conceived and supervised the study. MA, KL, and ASNR designed experiments and analyzed data. MA and KL performed experiments. MA and ASNR wrote the manuscript.
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