[초청강연] Lignin barrier for spatial restriction of pathogens in plant immunity

Roles of lignin-based barrier and autophagy in plant immunity

Ohkmae K. Park

Department of Life Sciences, Korea University, Seoul 02841, Korea

Plants are exposed to bacterial pathogens that have the ability to invade plant tissues and
proliferate in the extracellular space or apoplast. Plants have evolved the immune system to
recognize and limit the growth of pathogens. In spite of considerable progress in the study of
plant immunity, the mechanism how plants restrict pathogen growth remains unclear. In this
study, we report that lignin plays an essential role in plant immunity. We demonstrate that lignin
deposition readily occurs during incompatible plant-pathogen interactions and this process
requires Casparian strip membrane domain protein (CASP)-like proteins (CASPLs). CASPs
are known to be the organizers of the lignin-based Casparian strip, which functions as a
diffusion barrier in roots. The spread of bacterial pathogens is allowed and disease resistance
is decreased by defects in lignin deposition. Moreover, the motility of pathogenic bacteria is
negatively affected by lignin accumulation. These results suggest that the lignin-deposited
structure functions as a physical barrier, similar to the Casparian strip, trapping pathogens and
thereby terminating their growth. Moreover, our recent data show that lignin deposition is
dependent on autophagy. I will provide evidence suggesting that autophagy regulates the
transport of monolignols, building blocks of lignin, required for lignin barrier construction and
disease resistance.