Post-transcriptional β-1,3-glucanase gene silencing involves increased transcript turnover that is translation-independent

In tobacco line T17, basic beta-1,3-glucanases are silenced when a beta-1,3-glucanase (gn1) transgene of Nicotiana plumbaginifolia is present in a homozygous condition. Cosuppression of endogenous and transgenic basic beta-1,3-glucanases occurs via a post transcriptional process. This study shows that silencing correlates with a reduced stability of the transcripts encoded by gn1 and the co-suppressed endogenous glucanase genes. The observed decreases in mRNA stability at least partially explain the reductions in mRNA level. Furthermore, the results show that the enhanced, silencing-related turnover of gn1 mRNA does not require continued protein synthesis. The implications of these findings for the mechanism of gene silencing are discussed