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| Author(s): |
Juliana Cristina Baptista
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia |
| Defense date: | 2006-07-07 |
| Examining board members: |
Marcos Antonio Machado;
Celso Eduardo Benedetti;
Nelson Arno Wulff;
Julio Rodrigues Neto;
Suzete Aparecida Lanza Destéfano
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| Advisor: | Marcos Antonio Machado; Alexandre Morais Amaral |
| Abstract | |
The citrus canker, caused by the bacterium Xanthomonas axonopodis pv. citri (Xac), is responsible for considerable losses for the orange production, in Brazil and abroad. The disease is highly aggressive for citrus plants, resulting, among others, in injuries on leaves and fruits, with a reduction in the quality of fruits as much as in the productivity. Due to its importance, recently the bacterium had its genome completely sequenced and a number of open reading frames (ORFs) where identified by homology with protein sequences and annotated as associated to the infection process. Amongst them, some sequences that theoretically code for proteins involved in the degradation of the plant cell wall, which may indicate that the bacterium uses mechanisms related to this event during the process of adaptation and infection. However, there is no experimental data regarding such sequences to prove their real function during the pathogenesis of Xac. The main objective of this work was to identify functionally, in Xac, through in vitro and in vivo assays, genes involved in the production or transport of proteins related to the degradation of cellulose and, therefore, to analyze its relevance in the capacity of adaptation and infection of the bacterium. During the investigation, a collection of mutant strains of Xac was produced by random and site-directed mutagenesis, which were analyzed through the identification of leaf lesions and their action on degradation of artificial cellulose in plate as well as the growth in leaves. Through tests of mutagenesis and in vitro assays, this study shows that the xps operon that is present in Xac and encodes a type II secretion system machinery is functional and the genes XAC0028, XAC0029, XAC2374, XAC3516 and XAC4231 participate in cellulose degradation. In summary, for the first time it was experimentally demonstrated that Xac is capable in hydrolizing cellulose (AU) | |