SYSTEMIC ACQUIRED SILENCING OF A GUSA TRANSGENE IN APPLE

Abstract

RNA silencing is based on the processing of double stranded RNA into small RNAs by DICER-like proteins. These small RNAs guide ARGONAUTE-like proteins to complementary sequences resulting in posttranscriptional gene silencing. Silencing is a non-cell autonomous event. We used the binary vector pHELLSGATE8::gus containing nptII and a gene construct encoding for a hpRNA homolog to the gene gusA (sigus) for transformation of a ‘Pinova’ descendant, to evaluate the mobility of silencing for the first time on a woody plant like apple. 13 sigus transgenic apple lines were obtained. Following, gusA transgenic apple shoots were grafted onto sigus transgenic rootstocks in the greenhouse and in vitro. GUS staining assays revealed that the gusA expression in the gusA transgenic scion was clearly decreased in leaves and shoots compared to control shoots grafted onto non-transgenic shoots. Real-time PCR analyses showed that the reduction of gusA expression occurs on the RNA level.