The genome sequence of the plant pathogen Xylella fastidiosa

Abstract

Xylella fastidiosa is a fastidious, xylem-limited bacterium that causes a range of economically important plant diseases. Here we report the complete genome sequence of X. fastidiosa clone 9a5c, which causes citrus variegated chlorosis--a serious disease of orange trees. The genome comprises a 52.7% GC-rich 2,679,305-base-pair (bp) circular chromosome and two plasmids of 51,158 bp and 1,285 bp. We can assign putative functions to 47% of the 2,904 predicted coding regions. Efficient metabolic functions are predicted, with sugars as the principal energy and carbon source, supporting existence in the nutrient-poor xylem sap. The mechanisms associated with pathogenicity and virulence involve toxins, antibiotics and ion sequestration systems, as well as bacterium-bacterium and bacterium-host interactions mediated by a range of proteins. Orthologues of some of these proteins have only been identified in animal and human pathogens; their presence in X. fastidiosa indicates that the molecular basis for bacterial pathogenicity is both conserved and independent of host. At least 83 genes are bacteriophage-derived and include virulence-associated genes from other bacteria, providing direct evidence of phage-mediated horizontal gene transfer.

Genomic Insights into Xylella fastidiosa Interactions with Plant and Insect Hosts

“…The first genome of a plant pathogen, that of the bacterium Xylella fastidiosa, was only completed in 2000 (Simpson et al 2000). Since then, many bacterial plant pathogens have been sequenced, but much of the scientific knowledge extracted from these data is still limited, especially when compared to human pathogens.…”

Rooting of healthy and CVC-affected 'Valência' sweet orange stem cuttings, through the use of plant regulators

“…But the lower starch production, accumulation and translocation from leaves to the base of CVC-affected cuttings could have slower the root differentiation. X. fastidiosa promote the uptake of iron and possibly other transition metal ions, contributing to the typical symptoms of leaf variegation (Simpson et al, 2000). Gomes et al (2003a) working with three cycles of water deficit in healthy and CVCaffected 'Pêra' sweet orange plants found low IAA concentrations in leaves of diseased plants of the first cycle, but no difference in the third one, when plants were physiologically more damaged by CVC.…”

Genomics for all

“…Even more impressive are the indigenous efforts to create programs of genomics research in developing countries themselves. Scientists in the Brazilian Organization for Nucleotide Sequencing and Analysis (ONSA), launched by the state of Sao Paulo, successfully sequenced the genome of the citrus pathogen, Xylella fastidiosa 4 , and an expanded version of ONSA is nearing completion of the sequence of the dangerous human pathogen, Chromobacterium violaceum, as well as launching genome projects on schistosomiasis and sugar cane. The contributions of Chinese scientists to the sequencing of the human genome have been well documented 5 , and the Chinese National Human Genome Centre is collaborating on efforts to sequence the pig genome and the super-hybrid rice genome.…”