The plant pathogen Xanthomonas citri subsp. citri uses environmental light to modulate its virulence and counteract plant defence responses

KRAISELBURD, I.; DAURELIO, L.D.; TONDO, M.L.; CORTADI, A.A.; TALÓN, M.; TADEO, F.; ORELLANO, E.G.

Ciudad Autónoma de Buenos Aires

Simposio; 32 New Phytologist Symposium. Plant interactions with other organisms: molecules, ecology and evolution; 2013

New Phytologist Trust

Light is a major environmental stimulus that regulates plant responses against pathogen attack. Bacteria also have the ability to respond to light. Light perception is achieved through photoreceptors, including LOV (Light, Oxygen, Voltage)-proteins, sensitive for the blue region of the visible spectrum. Xanthomonas citri subsp. citri (Xcc), the bacterium responsible for citrus canker, presents a LOV-protein that we demonstrated to be a legitimate blue light photoreceptor involved in the light-regulation of bacterial adhesion to host tissues and in disease development. In this work, we performed an expression profiling in Citrus sinensis leaves upon interaction with the wild type Xcc and a mutant strain lacking the LOV-protein, using a Citrus cDNA microarray. We detected the principal biological processes differentially affected between treatments, which included photosynthesis, sucrose catabolism, secondary metabolism and defense response. We confirmed the results at the physiological level by histological and biochemical analyses of infected leaves. The genetic and biochemical evidence indicated that Citrus plants presented a more efficient response against the Xcc lov-mutant, suggesting that the LOV-protein participates in a bacterial strategy to counteract plant defense responses. These results represent the employment by the pathogen of an environmental factor important for plant defense, to successfully infect its host.