SGS3

SGS3 is a gene in the model plant Arabidopsis thaliana that encodes a protein involved in post‑transcriptional gene silencing (PTGS). The protein, often called Suppressor of Gene Silencing 3, is part of the RNA‑dependent RNA polymerase (RDR) system that amplifies short interfering RNA (siRNA) signals. SGS3 is required for efficient production of 21‑ nucleotide siRNA duplexes that guide the RNA‑induced silencing complex (RISC) to complementary mRNA targets, thereby down‑regulating gene expression.

Structurally, SGS3 contains a tetratricopeptide repeat (TPR) domain and a zinc‑finger motif that are thought to facilitate protein–protein interactions and RNA binding. The SGS3 protein localizes to cytoplasmic foci known as processing bodies, where it collaborates with other silencing components such as HEN1, HEN2, and DCL4 in the biogenesis of siRNAs. Loss‑of‑function mutants show reduced accumulation of siRNAs and increased expression of genes normally silenced by RNA interference, demonstrating the critical role of SGS3 in maintaining genome stability and regulating developmental genes.

In addition to its canonical role in PTGS, SGS3 has been implicated in the silencing of transposable elements and the regulation of defense responses to viral pathogens. The protein has been conserved among grass species, suggesting an evolutionarily important function in plant immunity and genome integrity.

Research on SGS3 has advanced understanding of RNA silencing pathways and provided a potential target for manipulating gene expression in crop species. The SGS3 gene remains a focus of studies on RNA‑based regulation and the interaction between genetic elements and their silencing mechanisms in plants.