Lipopolysaccharide O-antigen delays plant innate immune recognition of Xylella fastidiosa
Rapicavoli, Jeannette N.; Blanco-Ulate, Barbara; Muszynski, Artur; Figueroa-Balderas, Rosa; Morales-Cruz, Abraham; Azadi, Parastoo; Dobruchowska, Justyna M.; Castro, Claudia; Cantu, Dario; Roper, M. Caroline
Lipopolysaccharides (LPS) are among the known pathogen-associated molecular patterns (PAMPs). LPSs are potent elicitors of PAMP-triggered immunity (PTI), and bacteria have evolved intricate mechanisms to dampen PTI. Here we demonstrate that Xylella fastidiosa (Xf), a hemibiotrophic plant pathogenic bacterium, possesses a long chain O-antigen that enables it to delay initial plant recognition, thereby allowing it to effectively skirt initial elicitation of innate immunity and establish itself in the host. Lack of the O-antigen modifies plant perception of Xf and enables elicitation of hallmarks of PTI, such as ROS production specifically in the plant xylem tissue compartment, a tissue not traditionally considered a spatial location of PTI. To explore translational applications of our findings, we demonstrate that pre-treatment of plants with Xf LPS primes grapevine defenses to confer tolerance to Xf challenge.