A plant natriuretic peptide-like molecule of the pathogen Xanthomonas axonopodis pv. citri causes rapid changes in the proteome of its citrus host
B.S. Garavaglia, L. Thomas, T. Zimaro, N. Gottig, L.D. Daurelio, B. Ndimba, E.G. Orellano, J. Ottado, C. Gehring
BMC Plant Biol., 10: 51, (2010)
Plant natriuretic peptides (PNPs) belong
to a novel class of peptidic signaling molecules that share some
structural similarity to the N-terminal domain of expansins and affect
physiological processes such as water and ion homeostasis at nano-molar
concentrations. The citrus pathogen Xanthomonas axonopodis pv. citri
possesses a PNP-like peptide (XacPNP) uniquely present in this bacteria.
Previously we observed that the expression of XacPNP
is induced upon infection and that lesions produced in leaves infected
with a XacPNP deletion mutant were more necrotic and lead to earlier
bacterial cell death, suggesting that the plant-like bacterial PNP
enables the plant pathogen to modify host responses in order to create
conditions favorable to its own survival.
Here we measured chlorophyll
fluorescence parameters and water potential of citrus leaves infiltrated
with recombinant purified XacPNP and demonstrate that the peptide
improves the physiological conditions of the tissue. Importantly, the
proteomic analysis revealed that these responses are mirrored by rapid
changes in the host proteome that include the up-regulation of Rubisco
activase, ATP synthase CF1 α subunit, maturase K, and α- and β-tubulin.
We demonstrate that XacPNP induces
changes in host photosynthesis at the level of protein expression and in
photosynthetic efficiency in particular. Our findings suggest that the
biotrophic pathogen can use the plant-like hormone to modulate the host
cellular environment and in particular host metabolism and that such
modulations weaken host defence.
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