The XS (rice gene X and SGS3) domain is found in a family of plant proteins including gene X Swiss:Q9SBW2 and SGS3 Swiss:Q9LDX1. SGS3 is thought to be involved in post-transcriptional gene silencing (PTGS). This domain contains a conserved aspartate residue that may be functionally important. The XS domain has recently been predicted to possess an RRM-like RNA-binding domain [1] by fold recognition.

1: The XS domain of a plant specific SGS3 protein adopts a unique RNA recognition motif (RRM) fold. Zhang D, Trudeau VL; Cell Cycle. 2008;7:2268-2270. PMID:18635957