Differential gene silencing induced by short interfering RNA in cultured pine cells associates with the cell cycle phase

The double-stranded short interfering RNA (siRNA) molecules can silence targeted genes through sequence-specific cleavage of the cognate RNA transcript. The rapid adoption of technologies based on this siRNA interference mechanism has been a widely used method to analyze gene function in plants, invertebrates, and mammalian systems. In order to understand the dynamics of siRNA-mediated gene inactivation during cell division, we have investigated the relationship between the cell cycle phase and the post-transcriptional gene silencing mediated by siRNA in gfp transgenic Virginia pine (Pinus virginiana Mill.) cells. Among the different phases of the cell cycle, transgenic cells at the M phase gave 2-3 times lower gfp silencing than those at the G1, S, and G2 phases. The similar results of the siRNA-mediated gfp silencing were obtained in three transgenic cell lines. Differential gfp silencing induced by siRNA has been confirmed by northern blot, laser scanning microscopy, and siRNA analysis. These data suggested that siRNA-mediated gene inactivation is associated with the cell cycle phase in Virginia pine.