Plays a role in RNA-mediated gene silencing by acting cell-autonomously as a channel for the transport of double-stranded RNA (dsRNA) between cells. Mediates the spread of dsRNA and subsequent silencing of genes in cells distant from the site of dsRNA introduction. Selective for dsRNA. Preferentially binds long dsRNA, from 50 base pairs up to 700. Short 20 base-pair long molecules are not bound. May also bind dsDNA, but with lower affinity. Binding may be sequence-independent (PubMed:26067272). Required for avoidance behavior induced by small RNAs derived from pathogenic bacteria such as P.aeruginosa (PubMed:32908307). May self-associate to form multimers. Enriched at the cell periphery and also to the punctate structures of cytoplasm. Expressed in most non-neuronal cells, including body wall muscle cells. Expressed throughout all developmental stages. Absence of silencing in adjacent cells or tissues. Decrease in transgene silencing when combined with eri-1. This avoidance behavior is transgenerationally inherited, and thus progeny display this same aversion despite never been exposed to this pathogenic bacteria. Belongs to the SID1 family.