Manipulation of the defense response to Xanthomonas by RNAi in citrus

RAMÓN ENRIQUE, FLORENCIA SICILIANO, MARÍA ALEJANDRA FAVARO, NADIA GERHARDT, LUCIANO RIGANO, LORENA SENDIN, ATILIO CASTAGNARO, ADRIÁN VOJNOV AND MARÍA ROSA MARANO

Quebec, Canadá

Congreso; MPMI; 2009

Citrus is one of the most economically-important fruit crops in Argentina. The province of Tucumán is the primary lemon-producing region, with an annual output of approximately 1.3 million metric tons. Nevertheless, citrus commercialization in the region has been severely affected by quarantine diseases. One of the most detrimental diseases is citrus canker, caused by bacterial phytopathogen Xanthomonas axonopodis pv. citri (Xac). The majority of commercial citrus cultivars are moderately to highly susceptible to Xac. Our laboratory is developing a variety of biotechnology-based strategies for cultivar protection against Xanthomonas species based on interference with the biological and molecular processes of Xanthomonas pathogenesis. Post-transcriptional gene silencing in members of the Rutaceas family, achieved through interference RNA (RNAi), is one such strategy. Double-stranded RNA expression vectors, encoding hairpin RNAs for citrus phytoene desaturase and callose synthase genes, respectively, were delivered to lemon leaves by transient infiltration with transformed Agrobacterium. Phenotypic, histo-anatomic and molecular analysis showed that both vectors were functional not only in lemon plants, but also in other species of the Rutaceas family. This system has enabled us to manipulate the basal immune response in citrus plants, as well as the genetic expression in select signalling pathways and metabolic routes.