Differentially expressed stress-related genes in the compatible citrus-Citrus leprosis virus interaction

Leprosis, caused by Citrus leprosis virus, cytoplasmic type (CiLV-C), is the main viral disease in the Brazilian citrus industry. This occurs because of the widespread source of inoculum and the year-round presence of the vector, the tenuipalpid mite Brevipalpus phoenicis, in citrus plants. In addition, while some Citrus species are resistant to CiLV-C, C. sinensis, the main cultivated species in the country, is extremely susceptible to the disease. The main objective of this work was to identify genes in C. sinensis cv. Pêra plants that were differentially expressed after the host was challenged with CiLV-C. In order to accomplish that, cDNA libraries were constructed from healthy and CiLV-inoculated sweet orange leaves. Two hundred and fifty-four genes were found to differ significantly in terms of expression, with 193 of them induced and 61 repressed after inoculation. Here we discuss the possible roles of a sub-set of these genes involved in metabolism, energy, signaling and cell rescue, defense and virulence, and indicate which kind of response may take place in the initial steps of the disease. Although the symptoms induced by CiLV-C in its compatible interaction with sweet orange resemble those of hypersensitive response (HR) in incompatible interactions, our data indicate that, apparently, the manifestation of leprosis symptoms should not be considered HR.