IDENTIFICATION AND QUANTIFICATION OF DIFFERENTIALLY EXPRESSED GENES ASSOCIATED WITH CITRUS BLIGHT (Citrus spp.)

Brazil is the largest citrus producer in the world, being responsible for more than 20% of its production, which is, however still low due to phytosanitary issues such as citrus blight. Citrus blight is an anomaly whose causes still have not yet been determined, therefore there are no efficient control measures to minimize the production losses with the use of resistant varieties being considered the most appropriate method. However, little is known about the genes involved in the defense response of the plants to this anomaly. Considering that many physiological alterations associated with plant stress responses are controlled at a transcriptional level, in this study we sought the identification and characterization of the gene expression products differentially expressed in the response to the citrus blight. Through the suppressive subtractive hybridization technique, expressed cDNA libraries were built using mRNAs isolated from "Cravo" lemon tree roots (Citrus limonia L. Osbeck) under "Pera" orange (Citrus sinensis L. Osbeck) of healthy and sick plants. 129 clones were obtained by subtraction and their sequences were compared in databases. 34 of them linked to proteins associated to stress processes, while the others were similar to sequences of unknown functions or did not present similarity with sequences deposited in the databases. 3 genes were selected and their expressions were studied by RT - qPCR in real-time. Plants with citrus blight presented an increase of the expression level in two of those genes, suggesting that these can be directly involved with this anomaly. O Brasil é o maior produtor de citros do mundo, sendo responsável por mais de 20% de sua produção. No entanto, a produção ainda é baixa, em decorrência de problemas fitossanitários, como o Declínio do Citros que é uma anomalia cuja causa ainda não foi determinada e, consequentemente, não existem medidas de controle para minimizar as perdas na produção. O uso de variedades resistentes é considerado como a medida de controle mais adequada. Contudo, pouco se conhece sobre os genes envolvidos na resposta de defesa das plantas a essa anomalia. Considerando que muitas alterações fisiológicas associadas com respostas a estresses em plantas são controladas em nível transcripcional, neste estudo objetivou-se a identificação e caracterização dos produtos de expressão gênica diferencialmente expressos na resposta ao Declínio dos Citros. Por meio da técnica de hibridação subtrativa supressiva,