Among the major biotic agents causing diseases in citrus are found different groups of microorganisms elevating the production costs for the Brazilian citriculture. The problems are enhanced because the lack of genetic variability in the orchards, that are formed mostly by the rootstock Rangpur lime and few scion varieties (90% sweet orange 'Pera'). The genetic uniformity makes these plants very susceptible to pests and diseases. New varieties are necessary to increase the genetic diversity, and so, to get plants more resistant to important diseases. Genetic transformation is an interesting strategy for genetic breeding and its main advantage over the traditional breeding methods is the addition of interest genes without sexual recombination, avoiding undesirable characteristics. Among candidate genes to be used in genetic transformation, we can highlight WRKY transcription factors belonging to a large family of plant DNA binding proteins. The identification and characterization of CrWRKY17 and CitWRKY7 genes in the citrus genome allowed to classify them as members of the group II, subgroup d. Members of this group are involved in cross signaling pathways in response to biotic and abiotic stresses. Many studies have demonstrated the ability of WRKYs to bind with promoters regions of genes associated with defense, by interaction of WRKY domains with elements of response to pathogens named W box (TTGACT / T). Transgenic citrus plants overexpressing the CrWRKY17 or the CitWRKY7 genes were previously obtained and in the present work they will be evaluated in the interaction with the pathogens Citrus leprosis virus C (CiLV-C) and Xanthomonas citri subsp. citri, causal agent of citrus leprosis and citrus canker, respectively.
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