A secreted chorismate mutase from Xanthomonas arboricola pv. juglandis attenuates virulence and walnut blight symptoms.
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Date
2021
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Abstract
Walnut blight is a significant above-ground disease of walnuts caused by Xanthomonas
arboricola pv. juglandis (Xaj). The secreted form of chorismate mutase (CM), a key enzyme of the
shikimate pathway regulating plant immunity, is highly conserved between plant-associated beta
and gamma proteobacteria including phytopathogens belonging to the Xanthomonadaceae family.
To define its role in walnut blight disease, a dysfunctional mutant of chorismate mutase was created
in a copper resistant strain Xaj417 (XajCM). Infections of immature walnut Juglans regia (Jr) fruit with
XajCM were hypervirulent compared with infections with the wildtype Xaj417 strain. The in vitro
growth rate, size and cellular morphology were similar between the wild-type and XajCM mutant
strains, however the quantification of bacterial cells by dPCR within walnut hull tissues showed
a 27% increase in XajCM seven days post-infection. To define the mechanism of hypervirulence,
proteome analysis was conducted to compare walnut hull tissues inoculated with the wild type
to those inoculated with the XajCM mutant strain. Proteome analysis revealed 3296 Jr proteins
(five decreased and ten increased with FDR ≤ 0.05) and 676 Xaj417 proteins (235 increased in XajCM
with FDR ≤ 0.05). Interestingly, the most abundant protein in Xaj was a polygalacturonase, while in
Jr it was a polygalacturonase inhibitor. These results suggest that this secreted chorismate mutase
may be an important virulence suppressor gene that regulates Xaj417 virulence response, allowing
for improved bacterial survival in the plant tissues.
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Keywords
Hypervirulence, Juglans regia, Walnut blight, Proteome
Citation
ASSIS, R. de A. B. et al. A secreted chorismate mutase from Xanthomonas arboricola pv. juglandis attenuates virulence and walnut blight symptoms. International Journal of Molecular Sciences, v. 22, artigo 10374, 2021. Disponível em: <https://www.mdpi.com/1422-0067/22/19/10374>. Acesso em: 11 out. 2022.