Intranuclear gene silencing in Phytophthora infestans. The discovery that introduction of sense or anti-sense DNA sequences can lead to transcriptional silencing of the target gene opened the gateway to functional gene analyses in oomycete pathogens. Intriguingly, this study pointed to a diffusible trans-acting silencing factor that moves between nuclei and imposes silencing of the target gene in nuclei that lack the transgene. More information: