Performing Gene Constructs for the Silencing of Tristeza and Psorosis Viruses in Citrus

The citrus sector is the most important horticultural crop in Uruguay, accounting for the 95% of the fruit exports and being the third agricultural product in order of importance. Citrus Tristeza virus (CTV) and Citrus Psorosis virus (CPsV), together with the viroid for Exocortis and other viroids associated with this disease, are the viral and viroidal agents of highest incidence on citrus crops in our country. A highly effective strategy to control viral diseases is the induction of resistance by means of methods based on RNA silencing. RNA silencing is a mechanism based on the specific degradation of RNA, which is triggered by the presence of double-stranded RNA inside the cells. Recently, strategies to effectively silence any chosen RNA sequence have been described. Using constructs which are inserted into the plant genome and promote the formation of double-stranded RNA, it is possible to silence the expression of both endogenous genes and viral gene sequences. In this study, partial sequences of CTV and CPsV capsids were isolated and used to produce gene contructs that promote the formation of double-stranded RNA. These constructs consist on the insertion of sense and antisense viral sequences, separated by intron. The resulting constructs will be used in the genetic transformation of citrus in order to obtain plants resistant to these pathogens.