Molybdate uptake system of Xanthomonas axonopodis pv. Citri

55º Congresso Brasileiro de Genética
Resumos do 55º Congresso Brasileiro de Genética • 30 de agosto a 02 de setembro de 2009
Centro de Convenções do Hotel Monte Real Resort • Águas de Lindóia • SP • Brasil
www.sbg.org.br - ISBN 978-85-89109-06-2
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Molybdate uptake system of Xanthomonas axonopodis
pv. Citri contributes to virulence symptoms in grapefruit
Oshiro, EE1; Kim, J2; Siciliano, F3; Vojnov, A3; Wang, N2; Ferreira, RCC1
Laboratório de Genética de Microrganismos, Dept. Microbiologia- ICB II USP, São Paulo, Brazil.
Citrus Pathology and Bacteriology Laboratory, CREC- University of Florida, Lake Alfred, EUA.
3
Fundación Pablo Cassará, Centro de Ciencia y Tecnología “Dr. Cesar Milstein”, Buenos Aires, Argentina.
1
2
Keywords: ModA protein, TEM, Biolfilm, Xanthan gum, virulence symptoms, Citrus paradisi
Brazil is the largest producer of citrus in the world whose agribusiness has been affected by citrus canker. This
disease caused by Xanthomonas axonopodis pv. Citri (Xac) infect mainly orange crop and induce premature death.
The sequencing of genome of Xac opened perspectives to study of important genes belonged of physiology and
nutritional systems. The molybdate uptake system is an ABC transporter responsible to internalize molybdate. This
molecule is connected to cofactor called pterin and this complex (molybdopterin) is important to redox reaction in
carbon, nitrogen and sulfur global cycles. The aim of this study is correlate molybdate uptake of Xac with virulence
in grapefruit. Besides the regulation protein is lack in the molybdate uptake system in Xac, mutant strain in this
system has shown different virulence symptoms. The mutant strain was built by introduction of spectinomycin
and streptomycin cassette into the modA gene. The encoded protein ModA was unable to uptake the molybdate in
periplasmic space and this way can not delivery the molecule to permease in membrane plasmatic. The xanthan
gum production in mutant strain (XNmodA5) reduced twice and the biofilm became immature impairing the
adhesion. The images from transmission electronic microscopy (TEM) of the lesion in grapefruit have shown the
XNmodA5 strain living freely instead of condensed in extracellular polysaccharide matrix. The RT-PCR from RNA
extracted of bacteria grew in grapefruit has shown the rpfF and hrpG there were no difference between wild type
and mutant. Nevertheless, the gumB gene was less expressed in XNmodA5. Theses data clarifies the molybdate
uptake system role is more than nutritional and suggest an involvement in xanthan gum regulatory.
Support: FAPESP