Agricultural Microbes Genome 2 Conference Agricultural Microbes Genome 2 Conference
Poster: Cellular Processes, Regulatory Networks
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The complete genome sequences of the two bacteria phytopathogens, Xylella fastidiosa and Xanthomonas axonopodis pv. citri, have revealed many interesting features related to the genes involved in DNA metabolism. We have analyzed DNA repair pathways, once these genes are normally very conserved and keep homology across kingdoms. Since the Xylella and Xanthomonas genders are very close in the 16S rRNA phylogeny, we expected to have very similar machinery for the maintenance of their genomes. In fact, the comparison of most of the nucleotide excision repair genes (specially those related to UVRABC excinuclease), which are represented in both bacteria, confirms the very close similarity among the two genders. However, since the genome of Xanthomonas (approximately 5.3 Mbp) is much larger than Xylella (2.7 Mbp), it was not a surprise to observe non identical gene duplications in this and other repair pathways, although the products of such duplicated genes may play different roles in vivo, which remains to be investigated. Moreover, Xanthomonas present some DNA repair pathways that are completely absent in Xylella. In this regard, at least two genes merit mention: i) a photolyase-like gene indicate photorepair activity, and ii) DNA polymerase IV (dinB), that is related to error prone translesion synthesis in Escherichia coli. The existence of such DNA repair pathways in the free living Xanthomonas is consistent with a recent gene loss in plant parasite Xylella, probably due to its very restricted and specialized way of life in plant xylem. Financial Support: FAPESP (São Paulo, SP)