Splicing factor involved in post-transcriptional regulation of circadian clock and flowering time genes. Associates with the pre-mRNA of PRR7, PRR9, ELF3 and GI, and is necessary for the regulation of their alternative splicing and mRNA maturation. Probably involved in splice site recognition. Component of the spliceosome. Interacts with SR45. Expressed in roots, stems, seedlings, siliques, cotyledons, leaves, inflorescences, seeds and shoot apical meristem. Expressed in every developmental stage. Up-regulated by senescence. Expressed constitutively. Up-regulated by abiotic stress and abscisic acid. Longer circadian period. Severely dwarfed and infertile when homozygous. Belongs to the SNW family.