Measuring callose deposition, an indicator of cell wall reinforcement, during bacterial infection in Arabidopsis

The plant cell wall responds dynamically during interaction with various pathogens. Upon recognition of “nonself” components, plant cells deploy a variety of immune responses including cell wall fortification. Callose, a β-(1, 3)-D-glucan polymer, is a component of the material deposited at the site of infection between the plasma membrane and the preexisting cell wall that is hypothesized to serve as a physical barrier and platform for directed antimicrobial compound deposition. The defense-associated function of callose deposition is supported by its induction during pathogen-associated molecular patterns (PAMP)-triggered immunity (PTI) and its inhibition by defense suppressing virulence effectors. Thus, callose deposition is a commonly monitored read-out in plant defense. This protocol describes the use of aniline blue staining and fluorescent microscopy to measure callose deposition in bacteria-infected or elicitor-challenged Arabidopsis leaf tissues.