Coordinated Regulation of Pre-mRNA Splicing by the SFPS-RRC1 Complex to Promote Photomorphogenesis

Abstract

Light signals perceived by the phytochrome (phy) family of photoreceptors control gene expression at both transcriptional and posttranscriptional levels to promote photomorphogenesis. Recently, we identified a factor called SPLICING FACTOR FOR PHYTOCHROME SIGNALING (SFPS) that directly interacts with the photoreceptor phyB and regulates pre-mRNA splicing in Arabidopsis (Arabidopsis thaliana). To identify SFPS-interacting proteins, we performed an immunoprecipitation followed by a mass spectrometry and identified the Ser/Arg-like protein REDUCED RED-LIGHT RESPONSES IN CRY1CRY2 BACKGROUND1 (RRC1). Genetic analyses revealed that the sfps-2 rrc1-3 phenotypes are similar to those of the single mutants, suggesting that RRC1 and SFPS might function together. RNA sequence analyses of rrc1-3 identified a large number of genes whose pre-mRNA splicing is altered under dark and light conditions. Comparison of the sequence data revealed a subset of common genes coregulated by SFPS and RRC1 under dark and light conditions. Similar to SFPS, RRC1 also interacts with phyB, colocalizes in nuclear photobodies, and regulates light-dependent pre-mRNA splicing of a subset of genes. Taken together, these data suggest that although SFPS and RRC1 can regulate distinct subsets of genes, they also form a complex and coordinately control pre-mRNA splicing of a subset of genes involved in light signaling and circadian clock pathways to promote photomorphogenesis.