Study of XacPNP in Xanthomonas citri subsp. citri

BARCAROLO, M.V.; BETIANA S. GARAVAGLIA; FICARRA, F.A.; GOTTIG, N.; JORGELINA OTTADO

Bogota

Conferencia; Xanthomonas Genomics Conference 2015; 2015

Xanthomonas citri subsp. citri (Xcc) is the bacterium responsible for citruscanker. This phytopathogen contains a gene encoding a plant natriureticpeptide (PNP)-like protein (XacPNP) that shares significant sequence similarityand identical domain organization with PNPs and it is not present in anyother bacteria. PNPs are peptide hormones involved in regulation of ionsand water homeostasis. We have previously shown that XacPNP is involvedin plant-pathogen interaction modulating host homeostasis to the benefit ofthe pathogen, such as the improvement of host photosynthesis, renderinga healthier tissue that favors the survival of this biotrophic bacterium.However, a possible role of XacPNP on bacterial physiology has never beenstudied. XacPNP is synthesized as a preprotein and probably processed duringsecretion. We found that expression of the recombinant XacPNP precursorcaused bacterial lysis in Esherichia coli, and this effect was not observedwhen the predicted mature protein was expressed. Moreover, the expressionof XacPNP precursor in Xcc, and in a variant of Xanthomonas axonopodis pv.vesicatoria, impaired bacterial survival of both strains under saline stressconditions. These results suggest a possible role of XacPNP in the regulationof ion influx in these bacteria. The infiltration of a Xcc strain that expressesXacPNP fused to GFP in citrus leaves revealed that this protein is secreted aspredicted by bioinformatics and localizes on the citrus cells plasma membrane.These results suggest that XacPNP is secreted to exert its function and thatit has an effect on bacterial physiology in saline environmental conditions.