Effects of Xanthomonas citri subsp. citri Infection on Chlorophyll Pigment Content, Chlorophyll Fluorescence and Proteins Change in Citrus aurantifolia

Citrus canker has worldwide distribution and is still a devastating disease caused by the bacteria Xanthomonas citri subsp. citri (Xcc). With the aim of evaluating C. aurantifolia response mechanism, plant leaves non-inoculated and inoculated with the bacteria were collected in 1, 4, and 7 days post-inoculation. Consequently, the chlorophyll pigment content and fluorescence were determined, and proteomics study was conducted. Results indicated that pathogen infection, despite the negative effect on chlorophyll pigment content, improved the physiological condition. The maximum efficiency of PSII photochemistry and PSII quantum Yield (YPSII) as well as photochemical quenching increase were observed in infected plants compared to the control, whilst non-photochemical quantum decreased during infection. Judging by the results, the proteomic analysis revealed that these responses were mirrored by rapid changes in the host proteome that included the up-regulation of carbohydrate metabolism proteins and down-regulation of the ATP generating proteins during pathogen infection. The results indicated that the pathogen manipulates the host homeostasis by its effector proteins to exploit in its favor.