Plays a role in RNA transcription or processing during stress. Binds RNAs and DNAs sequence with a preference to single-stranded nucleic acids. Involved in mRNA alternative splicing of numerous targets by modulating splice site selection. Negatively regulates the circadian oscillations of its own transcript as well as RBG7 transcript. Forms an interlocked post-transcriptional negative feedback loop with the RBG7 autoregulatory circuit. Both proteins negatively autoregulate and reciprocally crossregulate by binding to their pre-mRNAs and promoting unproductive splicing coupled to degradation via the NMD pathway. Target of the Pseudomonas syringae type III effector HopU1. Mediates cell-to-cell trafficking of RNA interference (RNAi) signals (small RNAs (sRNA), e.g. small interfering RNA (siRNA) and microRNA (miRNA)) which regulate growth and development, as well as responses to environmental inputs, including pathogen attack; can compromise zucchini yellow mosaic virus (ZYMV) and tobacco rattle virus (TRV) infections at the early stage (PubMed:31812689). Interacts with TRN1 (PubMed:14756317). Binds to small phloem-mobile single-stranded RNAs (ss-sRNA, e.g. small interfering RNA (siRNA) and microRNA (miRNA)) in the phloeme exudate, including viral-derived sRNA (vsiRNA) (PubMed:31812689). Shuttling between nucleus and cytoplasm. Relocalization from the cytoplasm into the nucleus is mediated by TRN1 (By similarity). Observed in the phloem translocation stream (PubMed:31812689). Ubiquitous. Up-regulated by cold stress. Circadian regulation. Induced by hydrogen peroxide (at the protein level). The glycine-rich (GR) domain is necessary and sufficient for cell-to-cell movement and to interefere with zucchini yellow mosaic virus (ZYMV) infection. ADP-ribosylated by the Pseudomonas syringae type III effector HopU1. ADP-ribosylation reduces the ability of the protein to bind RNA. The triple mutant srbp1 srbp2 srbp3 is more susceptible to tobacco rattle virus (TRV). May be due to a competing donor splice site. Belongs to the GR-RBP family. Wrong choice of frame.