Required for constitutive and alternative pre-mRNA splicing (Probable). Involved in primary miRNA processing and pri-miRNA biogenesis. Binds both intronless and intron-containing pri-miRNAs (PubMed:26227967). Component of the spliceosome (Probable). Interacts with SNRNP35 (PubMed:15987817). Interacts with CYP59 (PubMed:16497658). Interacts with RCF3 and CPL1 (PubMed:24146632). Interacts with DRB1/HYL1 and SE (PubMed:26227967). A number of isoforms are produced. According to EST sequences. Highly expressed in roots and flowers. A presumably longer alternatively spliced form is found in leaves, stems and flowers. Mutant seedlings show increased sensitivity to salt stress and abscisic acid (ABA). The splicing pattern of the pre-mRNA is regulated in a tissue-specific manner and by development, and changes in response to various types of abiotic stresses. Belongs to the splicing factor SR family. RS subfamily.