Role of the Xf-0818 cellulase in the Xylella fastidiosa X citrus interaction. / Papel da celulase XF-0818 na interação Xylella fastidiosa X Citros.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

From the genome sequencing of the bacteria Xylella fastidiosa, the agent responsible for the citrus variegated chlorosis (CVC), studies on the pathogenicity mechanisms expressed during the occurrence of the disease were started in genomic function projects, aiming to confirm the function of the genic sequences identified in the project X. fastidiosa Genome. Among these mechanisms, the enzymes involved in the bacterium attaching process are highlighted. The present study had, as a goal, the orf denominated Xf-0818, cloned in Escherichia coli by means of the insertion into pET 28b(+) plasmid, which codifies a cellulase of a size nearly 60 kDa, possibly involved in the degradation of cellulose fibers present in the membranes of the xylem vessels of citrus plants. The degradation of this membrane would allow for the movement of bacterial cells among the xylem vessels, which would be important for the development of CVC symptoms. The enzyme was over expressed into E. coli by means of their induction using lactose and purified using ultra-filtration associated to metal affinity chromatography. The enzyme presented high activity over 1%-carboximethyl cellulose (CMC), which was evaluated through quantification of released reduced sugars. The antibodies were obtained by injection of the purified enzyme into mice, which were evaluated by using the ELISA. The enzyme activity over CMC was reduced after previous incubation with the antibodies. These antibodies represent a tool for the researches aiming the identification of conditions that favor the expression of this enzyme in vivo. The presence of gold particles on the citrus diseased tissue samples indicate the participation of this cellulase on the disease, but other studies using immunocytochemistry and mutants of X. fastidiosa are necessary to confirm this hypothesis.

ASSUNTO(S)

citrus variegated chlorosis emmunohistochemistry escherichiacoli xylen xilema expressão gênica genoma fruticulture genetic expression bactéria fitopatogênica escherichia coli genome clorose variegada dos citros fruticultura imunohistoquímica phytopathoghic bacteria enzyme enzima

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