The Brazilian citrus industry represents a important trade, responsible for global leadership in the market for frozen concentrated orange juice and not concentrate as well. Besides these products Brazil still exports by-products of orange (feed, pectin, oil), which corresponds to a total of 1.5 billion per year. However, Brazilian productivity is low, mainly because the incidence of pests and diseases. Among these diseases, the Citrus Variegated Chlorosis (CVC), caused by the bacterium Xylella fastidiosa is one of the most damaging for the industry. The damage caused by the disease are estimated at 122 million dollars a year, since the disease affects all varieties of sweet orange decreasing the production of concentrated juice. The disease is characterized by a reduction in fruit size due to the colonization of bacteria in the xylem of the plant, blocking the transport of water and nutrients to the shoot. The programs of genetic improvement of citrus are still a challenge due to the very low genetic variability and the breakthrough of pests and diseases. Thus there is a great need for expansion of the genetic bases and use of biotechnology tools coming to meet for this need. One such tool is the transfer of genes from any organism to obtain a desired trait in another organism, commonly called transgenesis strategy. Studies by our team have shown that mandarin varieties are resistant to X. fastidiosa, ie, did not show typical symptoms of the disease, besides possible reduce of the bacterial population in the plant. It was also shown by our team that some genes overexpressed during infection may be responsible for resistance to X. fastidiosa and consequently the control of CVC. Parallel to this, some chaperones known as heat shock proteins (HSPs) are known to be related to resistance to different stresses. Recently, the overexpression of a chaperone encoded by the gene soyBiPD conferred resistance to water stress in plants of Nicotiana tabacum. Since X. fastidiosa induces water stress in the plant and it is known that BiP genes also respond to elicitors of plant-pathogen response, this gene would also be useful in the control of CVC. Thus, the transfer of all these genes for citrus would be an excellent strategy, but there are many difficulties in the citrus transformation. Difficulties such as escapes, rooting, grafting, long crop cycle and many variations in response between varieties contribute to the search for alternatives such as model plants. Nicotiana tabacum and Arabidopsis thaliana are very interesting model plants for genetic transformation because they have simple protocols, short life cycle and high seed production. Moreover, it is known that N. tabacum is host to X. fastidiosa and Candidatus Liberibacter, the bacterium that causes Huanglongbing. Although it was recently reported that A. thaliana is host for X. fastidiosa. Thus, this work aims at the use of plant models as N. tabacum and A. thaliana for functional study of genes of citrus associated with resistance to X. fastidiosa.
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